I love Sonoma (it's better than most of Napa).
Montage, Ridge, and Jordan are all excellent and near Healdsburg. Of course there are many other wineries worth going to.
I have many thoughts about the City, although they tend to trend pretty nerdy. Seems like you'll be here for a few days. I'm happy to share them here, or via message, if you're interested.
Sam's is great. And if you don't have fog it will be beautiful. The aquarium in Monterey is really cool. The Wharf there is a little overly touristy, but it's still kinda fun. Don't know if you'll have the time, but 17 Mile Drive is spectacular. Worth paying the $20 or whatever it is to drive down to Carmel through Pebble Beach. It will be a bit of a haul from Healdsburg to Monterey. Are you stopping at the Muir Woods, or any other redwood groves? Muir requires reservations, but there are other (not quite as awesome) places to see coastal redwoods without a reservation.