I would separate them. With all that stress of new places, new noises, new smells, strange people, there's no telling who might get really upset and make an attack on the crate-mate.
Also, if for some reason you need to get one out, having one per crate makes it much safer - B will not escape while you're trying to remove A.
I would have a harness on each one, even crated. Start now getting them used to a harness. Have a leash for each one, so you can attach it to the harness as soon as you open the crate. Then no matter what, you've got some control. You may be needing your hands for paperwork and stuff. Do not leave the leash connected in the crate, it might tangle.
Good luck. My kid took a cat and a dog overseas in a move. Quite an experience.