NBR: Graduation Party site

Hello!  I'm looking to see if anyone has any ideas on a party room/location that could be inexpensively rented for a few hours for a graduation party.  Must be airconditioned and I could supply food if necessary.  I know a lot of restaurants have party rooms but they tend to get pricy and I'm trying to do this on a limited budget. 

I considered parks but I'm worried about the Aug heat.

Thanks so much!