M.D.
There's this new place in Menlo Park (borderline Redwood City) called UMe. It's only a few months old I think and everything is super clean and nice. From what i've heard it's pretty expensive though. I've never attended a birthday party, but there was one going on when we were there and it seemed like it was run well. My 2 1/2 year old son has a lot of fun when we go for open play.