2nd Birthday Party Location

Help! I am planning a birthday party for my 2 year old little boy in the San Fernando Valley (California). I have all the stuff and the entertainment, but no location. It is a Sesame Street Theme and we are going to have a puppet show. I would do it in our own backyard, but am worried the weather might not be so good. Our house is too small to hold all the guests so I need a place for 2-3 hours for aproximately 14 kids (and their parents), that isn`t too pricey. Please let me know if you have any good suggestions.