Rent an Inflatable
An inflatable can be a fun addition to a party.
Renting an inflatable bouncey, slide or water slide can be a great way to entertain young children.
You may want to consider purchasing an inflatable as well. Many are reasonably priced and can easily pay for themselves after just a couple uses. Purchased inflatables will typically hold less participants that their commercially available counterparts.
NOTE: When renting inflatables for a party at the park, there are additional things to think of such as policy for handling other kids coming over, and getting a permit that may be required (contact the Parks & Recreation department of the local government offices).
