I hope for your sake that they are all boys! You might want to take a spare pet carrier with you to the vets because if any of them are girls, you will want to keep them separate. And seen as you mentioned not being able to tell them apart, it might be best to separate any females at the vets as they are sexed. Is it an exotic vets you are going to?
Don't worry about them sleeping in other places! They will bed down where they feel comfortable. This morning I found 1 asleep under a wooden bendy log, 1 asleep behind a wheel and one wide awake running around
