Whenever I am doing scene shifts with my kids at the high school, or university level, I make sure I have pictures or layouts posted backstage. I have an overhead view of the stage, with the set pieces mapped out where they have to go, and then label the names of who is supposed to be moving what. Post these on both sides of the backstage areas and go over them with the dancers. Having a visual reminder will help when they are not 100% focused on moving the item, because hey- the dancing is going to be taking up most of their brainspace. So don't make them have to think too hard.
If possible, try to have the same people move the same things throughout the piece so it is easier for them to remember.