Park Chow: A good choice after a day at Golden Gate Park.
Chevy's: Free chips, ice cream and sombreros for the kids, margaritas for the parents.
Mel's Diner: An old-fashioned diner with balloons and crayons for the kids. 3 locations: Lombard, 1050 Van Ness and the original Mel's on Geary which was featured in American Graffiti.
Other restaurants
My niece liked Bubba Gump's when she was nine. The staff are very friendly to kids, and we liked the food, too.The Rain Forest Cafe, across the street from Pier 39, is also fun for kids, with animatronic displays and periodic rainstorms.
Max's: A deli gone wild. Big portions and a house rule that if your server ever asks you "Is everything all right?" you get a free meal. South of Market.
House of Prime Rib: Popular with meat-eating teens.
North Beach Pizza: Great pizza and a busy environment. North Beach.
More Things to Do with Kids in San Francisco: The Waterfront | Downtown | Golden Gate Park and Ocean Beach | Outside San Francisco

