Yes, bagging them up individually and putting them in a cooler is a great way to go. Keeps the temps very stable and protects them from sudden high temps as well as sudden low temps. However, for such a long distance which also means a long time in the cooler, you may also wish to get some cardboard inserts to section off little compartments inside the cooler. I have had friends who lost snakes because their bigger snakes moved on top of their smaller snakes and suffocated/crushed them, they can move around a little bit in their bags and the smaller ones seem to end up on the bottom unless there is a way to keep them more contained.