King Jim, Calistoga may be best bet if you plan on tasting a lot, since it is pretty close. Haven’t been there so no review. However, if you are up for a bit of adventure you might consider Olema RV Resort over near Point Reyes National Seashore. Olemaranch.com It’s about 25 miles from Napa, so the Napa area is a reasonable day trip. The “resort” is nothing special, but it is well shaded and cool during the summer, sites are pretty well spaced and it was quiet when we were there, plus, they have sites where you will fit. However, if you go you should access the resort from the North thru Petaluma with the bus. The road from the south left us with a choice of frequently crossing the centerline or rubbing the redwoods that line the road, and that was in our XL-40. Take the southern route in your toad, as it is beautiful.
The Point Reyes area is very cool (temperature and ambiance) and rarely crowded. If willing to walk, you will likely find completely deserted beaches in mid-week, beautiful scenery, a nice lighthouse, and history. (Sir Francis Drake stopped off there.) If you go, be sure to take the nature walk at the vistor’s center, which is the site of the epicenter of the 1906 San Francisco earthqake. You will see the remnants of a fence that crosses the San Andreas fault. The west side of the fence is about 30 feet north of the east remnant. A pretty sizable chunk of California lunged 30 feet north in a couple of seconds that day.