First thing I did was find a place to stay, Candlelight Inn, I booked it on line. http://www.candlelightinn.com/ Not too expensive in Napa terms.They have beautiful rooms, lovely grounds, a heated pool and a dynamite breakfast - that is included in the price.
Next and Most importantly, We visited the down town visitor center and spoke with Jim. After telling him that we had visited Napa before and we were not looking for 'Run of the Mill' he suggested a few wineries. We went to the Castello di Amorosa http://www.visitnapavalley.com/wineries-castello_di_amorosa_309.htm and to Nichelini http://www.nicheliniwinery.com/ . I don't know what you are looking for but I will suggest, as he did 'Go early and Go far first' making your way back thru Napa, It gets crazy busy!! The Visitor center will be able to suggest exactly the type of wineries for you to visit depending on your taste.
Tasting rooms are an option too http://www.trnapawineco.com/wineries.html
I knew that I wanted to have some Great meals, I am spoiled living in Montreal.
http://www.napatouristguide.com/restaurants-downtown.html so I ate at Zuzu and a sister restaurant of the same chef, La Taberna - my personal favorite. They are almost beside each other on Main street Napa. (Reviews of both can be found here on my blog) http://bigmamasnest.blogspot.ca/
I found a few top secrets http://www.budgettravel.com/feature/napas-top-secrets,5374/?page=1 and visited The Oxbow public market, a great place to pick up some food to take with you. At many tasting I heard "I need food!" Tasting a lot of wine requires food.
I had lunch at La Luna Market, it has picnic tables in the back of the store. Simple surroundings and good food (It is the place to pick up inexpensive spices) Both places are worth visiting!
The next day we went to Sonoma and I loved it! It is how Napa use to be, a gentler pace. We went to Chateau St Jean http://www.touringandtasting.com/destinations/sonoma-valley/chateau-st-jean/ and had wine and cheese in their rose garden. Then we visited Deerfield https://www.rexfamilywineries.com/xe/xe.asp?page=viewcat&cat=deerfield-ranch an Organic winery.
Your Napa/Sonoma Adventure can be any thing you want, Enjoy!