I never thought of this but at a company picnic my son discovered water balloons.
They put a bucket of water balloons and he loved it ! Ended up soaking wet but on a hot summer day like today; it was the best entertainment. So, I'm on my way to the dollar store to buy a bag of water balloons.
One thing, balloons are a choking hazard! Alhought I wasn't able to throw the torn balloons away here, when I do this activity I'm going to make sure I have a trash bag ready to pick up the pieces.