Another good option to consider is a gym or recreation center. Places like the YMCA, for example, often have rooms available for rent. Plus, the costs could be even lower if you're already a member of the organization.
See if there are physical activities and games available for you to incorporate into the birthday party itinerary, or access to any of the sports facilities. You can build a theme around the setting, like a basketball or swimming party. Plus, if you're expecting a rambunctious crowd, it's a great way to burn off some of that limitless energy.