There are no non-biting birds-- when a bird bites, you cannot scold the bird or yell or flinch, or you will just increase the biting. If you were getting bitten, it wasn't the bird's fault. As humans, we tend to project our desires onto animals, but it is very important that you read a bird's signals and not push the relationship before they are ready. Birds bite to communicate, so if you were bitten, it was trying to tell you something (e.g., I'm scared of you, you are too close to my mate, I don't want to be touched right now, I want attention etc etc). I cannot emphasize the importance of avoiding biting by reading signals BUT, WHEN (not if) you are bitten, you CANNOT react---most 8-year-olds (and most adults, for that matter) lack the self-control it takes to remain still and silent when a bird has drawn blood.....failure to do so will only increase biting behavior and the more a bird bites, the more likely it is to bite in the future. You must determine the cause of the bite (e.g., to get someone's attention, to get an object, to get put down or escape something undesirable like being held or being put back in the cage etc etc) and then you must make sure that your reaction doesn't provide the bird with the desired outcome. That having been said, you must spend months building your birds trust...and remember that trust is like a bank---if you do something to withdraw trust, you want to have a solid foundation of trust in the bank already, or you will go into debt...You will need to make more deposits to get back to where you were if you mess up and make a withdrawal. Do you get what I mean by that analogy?
If you personally want a parrot and have the time and energy to invest in one, then fine, but don't get one as a pet for your son under the assumption that there will be little work on your part (I know most parents anticipate picking up some of the slack when they get a pet for their kid, but think about what you might have to help him with if he had a dog and multiply that by 50). I am not exaggerating when I say that they are a TON of work (WAY more than a dog or cat--on par with a child). Parrots are flock animals and they are highly intelligent (even the small birds like parakeets and love birds). They are prone to self-mutilation, aggression and screaming when their needs aren't being met and since they have the intelligence of a 3-6 year old child (depending on type), it is very hard to keep them happy. They also bond closely with people (often one person). The bird picks who it likes, and it may or not be your son (it could be a neighbor or you or your husband). It is also extremely easy to train them to behave badly unless you have a solid understanding of their behavior....Birds can also over-bond with people and become dependent upon them to the point that they scream and self-harm when their "person" is not around.
Birds also live for a long time. Your son is currently 8 and with proper care, even the smallest parrot species is going to live for a minimum of 10 years....If he was upset by a biting bird (or you were), it is very unlikely that he (or possibly you) will remain interested enough to take on a 10+ year commitment that could extend well beyond his 18th birthday. **If** the bird does bond with him, then what will happen when he goes off to college and cannot take the bird with him? Even if you are willing to care for the bird, you will be no replacement for the loss of his person. This pet will end up being your responsibility (whether or not it bonds to you or your son)---not just yours, but the whole family's responsibility. You will all have to understand and follow certain rules when it comes to behavior. This includes the appropriate way to react when bitten, what to do when the bird screams (NEVER YELL BACK OR SCOLD)....the list goes on...
When my sister was 8, she begged for a parakeet and that poor bird was neglected terribly--not obviously neglected to the untrained eye--- (it always had food and water and a clean cage) but it was never tamed because my sister was too impatient to build trust and so she got bitten a lot and lost interest when the bird continued to show signs of fear and wouldn't talk. My sister was super-devoted for about 2-3 weeks, which is pretty patient, as kids go (sitting by the cage for hours, talking to the bird etc), but after awhile, friends wanted her to go on play-dates, the novelty wore off, and she gave up on trying to work with the bird. After giving up on bonding with the bird, she just stuck to changing water and food...She did that without a lot of nagging for about a year, but soon, the bare-minimum responsibilities (such as feeding/watering/changing liners) became a source of contention and they eventually fell almost entirely on my mom; especially when my sister was in high school ("Did you feed Granny?" "MOM-I AM GOING TO BE LATE!!"). We couldn't ever let the bird out of the cage because it would injure itself, so we had this sad, cage-bound, neglected bird who screamed all of the time, and was a general nuisance from my sister's perspective...At the time, my parents did not know what we were getting into and we had no idea that parakeets were as smart as larger parrots). My sister was also a very smart and responsible child...It didn't matter though because at 8, kids don't know what they want a year from then, let alone 10. She swore she would do everything it took to care for that bird, but she didn't know what caring for a parrot required (nor did my parents). We had many pets growing up and mistakenly had assumed that a parakeet would be like a hamster because they were sold next to each other at the pet shop and because the parakeet was cheap and is commonly portrayed as an easy family pet. These assumptions were terribly harmful to Granny, and looking back, we all feel so guilty knowing what we know now. Granny needed to be out of her cage and interacting with us, but she never got there due to our lack of knowledge and patience.
They move in slow-motion and can takes MONTHS to adjust to new people and changes within the environment. My bird wouldn't step up for 3 months. If you push them before they are ready, you will get bitten. Children do not generally have the patience required for dealing with parrots because they want a pet that likes them right away.
Parrots also get very moody and can be sweet one moment, then neurotic and aggressive the next. As a rule, they are not good pets for children (not just because they bite, but because they require as much work as caring for a child---if you wouldn't leave your son in charge of a 2-year-old child, then don't leave him in charge of a parrot).
When birds are babies, they are often sweet, but when they hit sexual maturity, they often change dramatically (in terms of preferences, but also in terms of increased biting etc). If you can deal with the personality of your adult bird, you will also be challenged 2x a year during breeding season (when aggression and moodiness increases significantly).
Birds need to have a set sleep routine (just like a child) and when they do not get their 10-14 hours of dark, quiet sleep, they can have health problems and behavior issues.
Birds are not good pets for cuddling (even though they may enjoy cuddles). Cuddling a bird or petting a bird on its back, under its wings (anywhere other than the head/neck) is a major trigger for hormones because it is very sexual to a bird. It sends the wrong message and can lead to all sorts of problems (biting, screaming etc).
They also need lots of time out of their cage each day and this is very important whether or not you work etc. You must make time for the bird every single day and you cannot just keep it in the cage because it is biting (or you will end up with a fearful, biting, cage-bound bird like Granny).
Finally, if you get a bird, you will have to be very careful about cooking and cleaning. Birds are extremely sensitive to chemicals and using standard cleaners or using products that contain Teflon/PTFE/PFOA can kill them (doesn't matter if the door is shut or they are on a different floor--the fumes can still kill them). Things like smoke, perfume, incense, air fresheners, cleaners, candles, burning food, paints, polishes, glues etc all produce very dangerous fumes. Their respiratory systems are completely different from ours and that makes keeping them in a home complicated.
Oh-- and, if you get a pair of birds, you are going to have an even harder time training them because, like I said, they tend to pick one person or bird. If you get a pair of bonded birds, you will be like the 3rd wheel. That having been said, if you get one bird and it picks its person, all other people who aren't "the chosen one" will have to work 10x harder to avoid being bitten etc. Yes, with proper training and socialization, some birds will accept more than one person, but acceptance isn't the same as being "the chosen one". When you have a single bird, you are the substitute for their entire flock, so you have to spend even more time interacting with them and including them in your daily activities.
There is so much more to say, but that is a good start. Please do not get birds and return them like that. They are very sensitive creatures who bond deeply and every time they are returned, their lives are turned upside-down and their trust in people is damaged. It is harmful to the bird long-term and creates lasting damage.