E.C.
you could also look into renting a room at a community center or local park (e.g. clubhouse at Arlington Park in El Cerrito) - then if the weather's nice the kids can play outside too!
facility rental info for El Cerrito parks and clubhouses at this site http://www.el-cerrito.org/services/pdf/rentals09-10.pdf. I know that when my kids attended Mustard Seed Preschool/Berkeley Covenant church in North Berkeley (near Monterey Market & King Middle school), the social hall was available to rent for things like kids birthday parties so that might be worth checking out too if it's a convenient location for you.