Until I locate the equipment, we did another experiment with baking powder in the balloon and soda water...
When you lift up the balloon, the baking powder falls in, a chemical reaction occurs and the gas blows up the balloon (that is the simplified version for a 7 and 3 year old of course).
One more thing on the christmas list - some cool science experiment books for kids!
I was inspired by this party (The princess and the frog blog) (seen on Party Perfect)
This is such a cool party.