Give a shout to my friend M. B. when you pass through Pleasanton.
Has anyone mentioned Mount Diablo yet?
For all the outdoor scenery you seem to favor, especially things like redwoods and coastal scenery and such, you should plan some extra time to explore north of the bay – Napa County, Marin County, Sonoma County. Others have already mentioned some of the places there.
You could drive between Highway 101 at Santa Rosa and the coast, passing through Sebastopol and Guerneville and lots of redwood forest. There’s a side road running out of Guerneville that leads to a state park in the redwoods with hiking, picnic areas and such. (ETA: It’s Armstrong Redwoods State Reserve.) There are plenty of such parks in that overall region.
On the coast in Marin County, there’s Point Reyes National Seashore. Plenty to see and do around there, including a visitor’s center. Approximately across the road from that on Highway 1 (and a bit south, I think) there’s an Audubon Bird Sanctuary area with some redwoods full of nesting herons, that’s open for a few hours at certain times. There’s a trail leading up a hill to a viewing deck well above the nesting trees, so you can look down on them from above. People there all talk in hushed whispers (if at all), so it’s like being in a cathedral.