We at Frisco Kids took a day off, and took the kids out on the town. Got home exhausted, but am typing this as I'm watching the Giants play ball.
On the other side of the Bay, you can get an Oakland Zoo family membership for $47 - normally $95. It's a great zoo, with a fun ride area outside the gates. And later this month, they have their annual Boo at the Zoo (though this membership doesn't start til November 1, so you'd pay ala carte for that). The membership includes a parking pass and guest pass, and a year's free admission for the named two adults, and any four kids. You'll also get some free ride coupons. Get your $47 Oakland Zoo Family membership here.