I don't know about wine country in December. It's wet and miserable up here this time of year, with three different storms lined up behind each other waiting to come in just this week. There's no grapes on the vines, and it's too cold to want to do anything outdoors. Maybe they can spend late morning in the Napa Valley, and get over to Sonoma after lunch and overnight there, and save a day on this side of the itinerary. Shouldn't be much tourist traffic this time of year.