I found the following in an article:
The advantages of throwing your children's birthday party outside are obvious: more space, no valuables or family heirlooms to be broken, tranquil atmosphere, and less clean up. Of course weather is an important factor when planning and you should try to check the local predictions. However, some parks have pavilions that can be utilized in case of rain, and can be reserved in advance of your party. I decided to throw the party at the Germantown Municipal Park because of its central location and facilities. The park was easy to access and had bathrooms, a large pavilion, 5 free standing Grills, a small fish pond, large shady oak trees, and a playground. More information about this park and others like it in Germantown, Tn can be found at: http://www.ci.germantown.tn.us/parks.html.
Choosing a Park and Making Invitations
It is important to have your guests feeling comfortable (especially during the Summer months) so visit several parks during the hours you think of having the party to see what areas of the parks are more shady than others. Check the park facilities and restrooms to make sure they will meet your needs and those of your guests. If you want to grill your food for the party, make sure there are grills or places where you can put your own. Once you have decided in which park you will be having your party, check with your local city's Parks and Recreation office for a list of rules and regulations. Some cities require that you tell them in advance that you will be throwing a party in their park, and if you will be occupying a pavilion they may require a deposit and rental fee.
Enjoy!!!!
Sandra