Congratulations on getting your chicks! I would make sure that the box you choose is not huge. I would line the bottom of it with straw or hay so they don't slide around on your drive home. Make sure it has a lid to keep them warm. Also, be sure that it has holes in it. Depending on the amount of chicks that you are picking up, a shoebox would work great. It sounds like a good idea to put a hot water bottle in it on the way to get your chicks. Then take it out when you put them in and they will be warm and toasty for your ride home. I would also recommend warming up your brooder before you leave to get them so it will be ready when you get home.
Enjoy your chicks!