Hi!
From what I understand from reading what the landlord said, RC specifically wanted a larger trailer so his kids could have rooms to themselves. I've read some speculate that maybe due to his working night shift, and Haleigh's fear of the dark, that the kids may have been moved to their room temporarily.
I kinda think, and this is just my opinion, that somebody, somewhere along the way had made a threat to do some harm to RC's family...which would explain the kids sharing a bedroom with them, and it would explain RC's belief that someone stole his daughter during the 911 call....
hope that makes sense...