Jill's savvy followup to the kid bedroom/guestroom hack is a hack unto itself:
When we have guests coming to visit and I know my boys will be displaced from their room, I have them pack a suitcase of clothes for the duration so they don't have to keep going into the now-guest room to get dressed. It just became part of the process of moving the trundle closer and getting out the guest sheets, etc.
Fave toys, blankies, books, etc. could go into the suitcase as well!
Speaking of suitcases — check out Trunki, a hard-shell suitcase kids can ride through the airport. I got a PR note about this a while back and have been meaning to look into it further. Sure is cute, but does anyone have one who cares to comment?