E.S.
I recommend Montclair park on Moraga Blvd. in Montclair. We just had my son's 2nd birthday party there. You can reserve tables. There's a pond with ducks and geese and two playgrounds - one for kids under 5 and one for older kids. There's also a mini stagecoach with "horses" the kids can climb on. The bathroom facilities are not great, but it is a park after all. And we had pizza delivered from nearby Cybelle's - they delivered to the park at 11:30 a.m. which was nice. It's a nice park and there are picnic tables in shady areas and some in sunny areas.