Secret Dining Room Cave
My children were campaigning to set up the tent inside recently, but instead of fishing it out of the attic, I threw a tarp over the dining room table to turn it into a cave. This was worth a lot of entertainment, and was only annoying because they brought lots of stuff down from their rooms for it and our new dog decided to try to steal those things, one by one. But, at least it kept all three of them (dog and kids) happy. It also had the interesting effect of turning my children into snakes who came hissing and slithering into my office periodically, but pre-school snakes are actually very cute and it sure beats the alternatives—draping themselves on me, or fighting! All in all a very successful activity.