Balloon game: two people stand across from each other and hit a balloon into the air. Then you have to run to hit the other person's balloon back into the air before it hits the ground.
Balloon Puppies - super easy and lots of fun! The toddler LOVED them. Of course, 5 minutes in, I popped it, and had to make another one and convince him it was the same one.
Beat the Heat with Water Balloons ~ Learn Play Imagine
Simple Science - Discover how many balloons can lift a bag
Crazy hair day idea
DIY Balloon Cannon - a simple, active, and entertaining boredom buster for kids from And Next Comes L
30 Ways to Play with Balloons | hands on : as we grow
For the child who enjoys tactile experiences... balloon squishy balls! Lame. Hard to get into the balloons and Atticus' hands are not strong enough to squish it. I found it hard myself in fact.