Double64Double
Great for kids of all ages from 2 to 100. A "must" for those with kids in the area. Clickity-clack through the park - through the tunnel, smell the smoke from the engine, breathe in the fresh eucalyptus and bay scented air. Combine it with a trip to the Merry Go Round. Unfortunately, the Little Farm is currently closed, but you can enjoy a short walk down the boardwalk to Jewel lake as well.
suemap
She's only 2 (but precocious of course) and just couldn't get enough of this train. We almost missed the museum, but caught it as we were leaving. It was entertaining for the adults in our party. But we all enjoyed riding in the little open cars around the bends, inside the tunnels and through the woods. The drive up the hills to get here was a thrill in itself; we pulled over to enjoy the beautiful view of SF bay (which are not available from the train).
azephyr
My young kids loved riding this small scale railway around the hillside. There isn't a lot to do besides the train, but the engines and carriage cars are charming.