OUTDOOR SPACE GAME IDEAS: 50 outdoor summer activities for your kids to check off! A bike obstacle course, a water balloon pinata and glow in the dark bowling sound like tons of fun to me!
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.