I prefer Sonoma to napa. Easier to get to/from the city and the vineyards are much more chill. If you've got some ladies with you it's not bad to hit a table at Gloria ferrar for some bubbles to kick things off. Then I head to Larsons, which is the vineyard I belong to. Usually pickup food from the Fremont diner which is less than a mile away. Be aware that there's usually a wait so best to try to get there early or go place your order then post up at Larsons and have someone swing back 30 minute later to grab your order. Food is legit.
Anyway, I like Larsons because they have cornhole, ladder golf, bocce (although not a great track), you can walk through the vines, etc. usually groups of schmokes running around all tips in their sundresses.
gundlach mentioned above is also nearby and solid setup to post up looking over a man made lake.