When our son (easy child) went to the local college (dorm), I converted his room into my office. It was a little sad. I have a really nice couch in there that opens up. Some of his furniture went with him and some went into the garage and one piece went into difficult child's room.
Then, difficult child moved out. I changed that room into a guest room. That was easy child's original room, actually. It is on the large side and has a bathroom in it.
It has a large dresser in it that was originally difficult children. Some of the finishings were originally from easy child's day.
I have a really beautiful bedspread on the bed and decorated in very nicely. I also have a treadmill in the corner, weights, etc.
When difficult child and easy child come over, both of them like using the room.
I do have a bit of an issue if they both come at the same time!!!!
UGH! I'm working on rectifying it as best as I can.
It was "hard" for everyone in a way when I redcorated, but it did send a message. I was as gentle as possible. Both adult children know that they are always welcome to stay at my house under certain circumstances, for a finite period of time, and if they follow household rules (nothing harsh, etc.). We try to have a good time.