Sounds like a real ordeal. Cats will naturally head for a "hidey hole" when insecure. It's better to let them have what they want so they can gradually get used to the new home. Let them get into their own carriers any time they want. They will appreciate the private little home of their own until they feel safe in the new surroundings.
We have a hole our cats can get down into that goes behind the couch so that's where they were whenever they were insecure. That changed in time.
We are about to set out with 2 new cats...the other 3 have been gone for years. We will keep them in their carriers while rolling and just open the doors when we park and let them exit and explore as they will. The cat box, food and water will be where they can easily find them.
It's never good to force things on any animal.
Our young dog has never RVed either so, all 3 of the critters are in for a new experience and we fully expect to have issues and restless nights for a while!