[Mz]

Muir Woods -- It has redwood trees, which are a "must see" if you go to Cali, and it is local to the SF bay area, unlike most of the remaining redwoods (which tend to be out in the middle of nowhere).

The big park in SF has an aquarium and an oriental-style garden. My kids thought the aquarium was a big yawn (after visiting the huge, world-class one in Tennessee, all other aquariums were forever ruined for them) but really liked the oriental garden, which was a new experience.

Just drive around SF. It is the only large city I have been in on two continents that made me go "Wow. I wish I could live here." The city itself is amazing.

Six Flags has a theme park in Vallejo: http://www.sixflags.com/discoverykingdom/index.aspx I never went to it (I'm not a big fan of theme parks) but you did ask about theme parks.

Point Reyes is unique. I never made it out there (unfortunately). It is a piece of the Pacific Plate that is above water. The land is, therefore, geologically distinct from most of California and this helps contribute to a unique ecosystem with (IIRC) some species unique to that little piece of land.