If you like baseball, but the drive (or train) to Pac Bell Park (or whatever it's called these days) is too long, take the kids to a home game with the San Jose Giants. Tickets on Groupon today are $5 (normally $10). They're good for any home game in the 2010 season.
Get 4 tickets to Playland Not-at-the-Beach in El Cerrito, for $25 (half-off) via the Savvy Source. It's open weekends in El Cerrito and is an old-fashioned amusement place, with 30 pinball machines set to free play, arcade games, live magic shows, carnival games, and a miniature hand-carved circus. It's set in 9,000 square foot building and is a non-profit. In August, they'll have a Pixar Tribute and Pirate Weekend. September’s weekend events include: Playland Lives on Forever!, Playland’s Adventure Weekend and a celebration of the famous IT’S-IT ice cream bar, including free IT's-IT ice creams. (I love these).