T.Y.
give them a time to say goodbye to their old room,even their toys and pillows and everything else...say goodbye to the old room , then when you move or even before, bring all those things above(if possible) say hello to their new room.Let them feel that it is a group effort(esp. the 2 of them) doing a group project(goal is togetherness).As Winnie the Pooh says,It's always good to eat/play when there's a friend or sister with you... good luck and have fun! My girls were 5 ans 3 y/o when we moved and they loved the process ,to the point that even Mom and Dad joined them in saying goodbye to every nook and corner that the kids thought of saying bye to.