I take my Sunny out in a Petsfit backpack carrier frequently. My Sunny
is quite tame, and she loves it. My budgies - when I take them out, they merely tolerate it. However, I think it's good for them anyway. I think it's really a great idea to take her out with you. You mention "long walks;" you might want to start with one or two shorter walks so she can get the idea.
When I take my Sunny out, I load up the little food dish with her favorite treats. I'd suggest you make sure to do this, especially at first, so she associates her backpack-carrier with Good things.
Also -- pay attention to the temperature, and her comfort in general. IF going for a long walk, try making it a circular route so at any given time you are not Too Far from either your car or your home etc.
*Don't* wear extra layers if it's chilly; you want to become un-comfortable if she would. Also, as it gets warm, pay attention because she can get over-heated in her carrier before you. So if it is hot out, doN't dress Too Lightly either; again, you want to become Un-comfortable Before she does.
The other day I was planning to take my Sunny for a walk on a rail-trail across a bridge. However as I approached I could feel the chilly water-breeze, and knew if I continued, she would be feeling that chill for far too long before I could return, so, I turned back right then.
That is my advice. I don't think she will get too stressed -- however, you know your bird best; pay full attention and if she does seem stressed, take her back home and calm her. If you are driving back home, then play some relaxing music for her on the way.
