1) Cut string about 6 feet long.
2) Tie one end of string to chair.
3) Thread string through straw.
4) Blow up balloon. DO NOT tie it.
5) Pinch balloon with fingers so air doesn't escape.
6) Attach balloon with two pieces of tape over (running the tape over the straws and over the balloon).
7) Release balloon!
I used three strings so the kids could each race a balloon. They really enjoyed it. I don't know about your kids, but there is nothing funnier to my kids than the sound of a balloon loosing it's air. :)
(Video of the big balloon race!)