Good call not staying Napa (Disneyland of Wine). You should drive over one day just to check it out. Specifically , the Silverado Trail is beautiful. Make an appt. at Joseph Phelps and you will taste good wine and have one of the best views in Napa. If I do Napa, I start early 9:00 or so to mitigate the crowds. Beringer and Mondavi start at 9:00am in their reserve rooms which I would recommend shelling out a little extra. Also, consider making appts. at the wineries you really want to visit if not open to public. Resto reqs include AD Hoc, Bouchon Bistro, Bottega. If you want to get fancy with great view and great food....Auberge Du Soleil. Not cheap.
Sonoma. I prfre to focus Dry Creek Valley and North. You get out of the crowds that way. Healdsburg is a great town to use as a base. Dry Creek Kitchen in Hotel Healdsburg is tasty. My favorite place is Bistro Ralph on Healdsburg square. Think Chardonnay, Pinot Noir in Sonoma County and Cabernet, Merlot and Chard in Napa if that helps guide your winery visits.
Enjoy