Inflatable Trampoline
Trampolines for sale online. Use an inflatable trampoline for less risk of injury to the kids. There won't be the heavy pices of metal for them to hit their head on. Besides that, the inflatable trampolines are usually cheaper. The kids will get lots of needed exercise on one of these trampolines. Everybody jump.
For more useful water inflatables check out the inflatable island page.