A quick trip to the dollar store will get you all the supplies you'll need for an afternoon of balloon-swatting. For each bopper you'll need
a car wash sponge and a bag of balloons. Pick up a free paint stirrer from the hardware store or your own garage!
Sand the paint stick so there are no splinters and paint if desired. Use a serrated knife to cut a slit into the center of the sponge on one end, and cut a depth about to the middle...please don't cut your hand! Spread some hot glue on the end of the stick and push it in.
Blow up a few balloons and let the kids go crazy...but not too crazy :) Not bad for a dollar per person and some balloons. Hope you'll try it!
If you want to do this activity outside, consider getting a larger, heavier blow up "punch ball" as it won't be so easily lost in the breeze.