Hearst castle is a great spot, but since you mention wineries, the main area is 'wine country' towards Napa, and there is a actually a European style castle towards the top of napa valley with its own wine tasting that's good. There's also a 'Napa Valley Train' with an elegant ride in the valley and gourmet meal:
http://winetrain.com/
I'd say it's tricky to 'do' SF well - one tip, Golden Gate Park - it has a great science museum with a Planeterium/indoor rain forest/amazing aquarium; and another museum for Art that's one of the more visited in the US, the De Young. And it's a beautiful park as well.
Going north is great - Muir Woods and Sausilto are right across the Golden Gate with a bunch of nice 'small towns' and even better, perhaps, coastal views.
I don't recommend Fisherman's Warf, 'tourist trap', but there is the Ferry Building with dozens of gourmet shops that's nice and relatives I took loved it. For an idea, it has two stores just for oilve oil... also plenty of good food from Scharfenberger's chocolate to Gelato to cooking stores to a Farmer's market three mornings, on the water.
Of course there's too much gourmet dining to talk about, but places like Boulevard and One Market near the Ferry Building are great.
There's even a 'scenic 49 mile drive' that starts at City Hall if you just want to see a lot of neat places.
China Town is one of the biggest outside China, North Beach for Italian.
Not sure you would want to see a play when you have New York for that.
Just for a taste of California, pun intended, you might like to check out a Trader Joe's of dozens in California, unique food for good prices.
There's a Cirque Du Solei show that might still be going in April in San Jose called Totem.