When I have one or two projects on my design wall & no room for anything more I lay blocks out on the floor. You have to walk through my sewing room to get to the kids play room (both in the finished basement). My kids know the drill, they just tip-toe very carefully over my project & straignten it if they mess it up.
No matter how bad my sewing room looks, the play room is always worse, so it's all good.