Here are my recommendations from the few times I have been to Napa/Sonoma.
V Sattui Winery – http://www.vsattui.com
–My favorite Napa winery. Also where my brother got married last summer. They have a beautiful area to picnic. Brink your own or buy food from their on-site and very well stocked market.
Peju – http://www.peju.com/
–Beautiful grounds and some pretty fountains (the wine is really good too
Bell – http://www.bellwine.com/
–They have great award-winning Cabernet Sauvignon. Also have tables outside to picnic and some Bocci courts to use.
We have stayed at the Embassy Suites in Napa…very nice hotel. Large rooms, beautiful grounds, and the free breakfast buffet as well as managers reception in the evening are perfect bookends to a day of tasting. http://embassysuites3.hilton.com/en/hotels/california/embassy-suites-napa-valley-NAPVLES/index.html
Ferrari Carano – http://www.ferrari-carano.com/
–My favorite winery in Sonoma, there is an upstairs tasting room and the Preval tasting room in the basement. The Preval room is more expensive to taste but the wines are better too. You can also (if planned in advanced) set up a food/wine pairing for not much more $ than a Preval tasting would be. Info should be on their website. They also have very pretty grounds and gardens.
Korbel Winery – http://www.korbel.com/
–Great free tour of their facilities and how they make champagne (sparkling wine) plus a free tasting at the end of the tour. They taste and sell some unique champagne (sparkling wine) that you can only buy at their winery because of the limited quantity they make it in.
I have stayed at the Dry Creek Inn (Best Western) in Healdsburg and found the accommodations quite pleasant.
We ate dinner one night at Zin restaurant in Healdsburg and had a delicious dinner with some fantastic wine. http://www.zinrestaurant.com/