How many birds are you talking about?
Although I only have my ringneck now for 3 months she already has 1 000's of kilometers behind her. We travel to our house by Kruger ones a month and it is a 4 1/2 hour drive.
We used to travel at night when all my reptiles are asleep but this did not work for Sterretjie (her first trip). She just could not fall asleep but did sit on my husbands shoulder all the way without giving any problems. She does not like my husband but I was occupied with my iguana who always sleeps on my lap during these trips - his choice.
We took all the other trips during the day and she seemed to love it. I placed a towel over the backrest of the seat so that she does not damage it, gave her toys to nibble on and one of those sweets that you buy for parrots that has the sunflower seed - honey etc. The sweet kept her busy ALL the time. My iguana and bearded dragons were on the move, giving me hell, but this did not bother her at all, nor did she seek any attention from me.
The view out the window and the sweet was all she was interested in.
Another guy that I know has 2 macaws and they travel everywhere with him. Each one has their own swing, draped with sweets, on the back seat looking out the window. They even sit still during the times that his husky rides in the back.
As long as they have a view out the window and something to chew on, then they are happy.
I would suggest that you first take them for short drives to the shop etc. so that you can see their behavior, you might discover that they have to be caged. All animals, birds, reptiles etc. are not the same, what mine like yours might hate. Observing your birds closely is the only way to get to know them as individuals, each ones needs, likes and dislikes. After you have done that you will be able to
make sure they are cared for in every way!

