Cool the kids off with a homemade sprinkler. Take a 2 liter soda bottle, poke holes in it. Attach to a garden hose via a male to male adapter that cost less than $5 at Lowes. Toss over a tree branch and let hang. You can adjust how the water sprinkles by adjusting the water flow. When the bottle gets stupid, just switch it out with another bottle, no additional cost!