Relatively close to Walnut Creek is the
Blackhawk Auto Museum. I did it in 30 minutes, but I have the attention span of a cranky two year old.
I have endless advice on wineries and restaurants in the North Bay (and SF). For wineries, to quote Tommy Smothers, "Napa is for Auto Parts, Sonoma is for Wine." As a Sonoma County Vintner my advice is hopelessly biased.
Domaine Carneros has a nice setting; Other sparkling options are Gloria Ferrer (close to Sears Point) and J Vineyards (nice tour). NOTE: Sparkling has become quite popular such that many wineries are offering a sparkling option. The vast majority are produced in a custom crush about 5 miles from my home (because specialized equipment is needed). If you are going to visit a domestic sparkling house, find one that produces in-house.
If you visit Napa for wine, consider Frank Family, Corison, Bouchaine, Sinskey, Chateau Montelena.
Sonoma County Winery options:
Lambert Bridge - Healdsburg/Dry Creek
Ridge Vineyards - Lytton Springs. Iconic California Legend; nice tours
Passalacqua Winery
Arista Winery
Copain - Windsor
Gary Farrell - RRV - beautiful setting
A few Sonoma County restaurants:
Chalkboard - Healdsburg
SHED - Healdsburg
Barn Diva - Healdsburg
Campo Fina - Healdsburg
Diavola - Geyserville (great wood fired foods, no reservations)
SingleThread - Healdsburg (an extreme splurge, but worthwhile)
Brass Rabbit - Healdsburg
Valette - Healdsburg
Glen Ellen Star - Glen Ellen
The Girl and the Fig - Sonoma
The Spinster Sisters - Santa Rosa
Jacksons - Santa Rosa
Bistro 29 - Santa Rosa
K&L Bistro - Sebastopol - French Bistro
There's a nice
beer/cider scene evolving at The Barlow in Sebastopol
If I'm eating in Napa, the I go to Bouchon, Ad Hoc, Redd Wood, Oakville Grocery (for sandwiches), Gott's Roadside (big lines on weekends), Lovina.
I have links to the restaurants/wineries, easier to paste into an email if you are interested.
Have a fun trip.
Don