baking soda and vinegar have long been good friends of mine for cleaning around the house, but hudson and lucy have befriended them too, as of late. this is a perfect outdoor activity that requires pretty little in the way of set up or clean up. just throw down a few interesting containers, a couple of sets of measuring spoons and let the little ones have at it.
they get the most mileage from vinegar in a squeeze bottle, as opposed to a large pitcher which seems to make flooding the table just irresistible. my only rules are no fighting and when it's gone, it's gone. they're learning how to conserve.
both baking soda and vinegar can be gotten in bulk, for cheap, at costco. we tint our vinegar with liquid watercolor that i buy at discount school supply. because, you know, bright pink foam is way, way cooler than white. for extra kicks toss in some glitter.
my kids would do this every day, if i let them--how are you keeping your kids busy???