Are you looking for a fun game to play that will keep the kids busy? These Balloon Cup Shooters are awesome! And they will definitely keep the kiddos entertained for a few hours. All you need are plastic cups, balloons, duct tape and ping pong balls.
Balloon Rockets - I've done this in several science camps I've conducted. Kids have fun with it. But, when the balloon deflates it may fall off the straw because it's surface area changes - another good thing to show and explain to kids.