I have been meaning to reply to this, sorry it took me so long.
All the advice you have been given is excellent.
I made a similar move from Engand to Canada. At the time, we had three dogs and two cats. In my case, I considered the animals' temperaments, but also what I could cope with, traveling, and once I got here. (I was traveling alone with a new baby)
I ended up finding new homes for two of the dogs, and one of the cats. It was heartbreaking at the time, but it was the best situation for the animals, and us.
So, I brought one dog and one cat here. I think the dog, an Old English Sheepdog, was about 3 years old, and the cat was maybe about 5. So, much younger than your cats.
The animals really do adapt well, though. Once they get here they have
you with them. As has been said, give them access to a small area at first, and gradually expand the space, so they are able to roam throughout the house. Start by putting the travel crate in that room, open the crate door, and let them take their time to explore.
By far the most stressful part of the move, is the journey. So prepare for that ahead of time. Introduce them to the crate they will be traveling in, ahead of time.
There are very strict regulations about crate sizes, and lots of documentation you'll need from the vet, on the animals' health, before you can bring them into North America. At least this was the case when I brought our animals here.
I'm sure I'm telling you something you already know, but all this preparation needs to be done well in advance. In the case of bringing our animals to Canada, it was also very expensive.
As I said, animals are really good at adapting. Even with a 24 hour delay at Heathrow, and the animals having to be unloaded from the plane, and put into an RSPCA shelter overnight, to wait for another flight, they arrived safely, and did very well here. It took them a matter of days to adjust.
Good luck, whatever you decide, and all the best in your new life.

dg