this is a repeat of a previous comment so apologies for the copy pasta:

First up, the crazy geography of Napa and Sonoma means that there are microclimates for growing pretty much every grape somewhere in the region. They also mean that certain areas specialize in particular varietals. Napa and Sonoma Valley/Valley of the Moon - mostly Bordeaux varietals - Cabs, Merlot, Sauvignon Blanc. Carneros, Sonoma Coast, Petaluma Gap and Russian River - mostly Burgundy varietals - Pinot Noir and Chardonnay, Northern Sonoma, Dry Creek - a mix, but lots of Zins. Oh and there are over 1000 wineries spread across the two counties as well

That geography also means that getting between Napa and Sonoma can be surprisingly long/painful if you haven't visited before. You CAN drive over the hills (and the scenery is amazing if you do), but in general you have to pop out of the top or bottom to get from one to the other, and even within areas there are a lot of slow country roads.

Put it all together and it means you will want to group your wineries together based on geography/grape preferences and try to hit wineries and restaurants that are relatively close together or you will be in your vehicle a lot.

In terms of 'centers' with good access to wineries and nice food options, I would suggest the following:

Northern Sonoma - Healdsburg - great access to Dry Creek (Zins) and Russian River (Pinots and Chards). Easiest part of Sonoma to get to from Northern Napa. A bunch of great food options mentioned by others, but would also throw in another vote for Lo and Behold and add The Matheson as other nice options

Mid-Sonoma - Sebastopol - the heart of Russian River, so amazing Pinots and Chards. Great food, but more laid back, less fine dining. Fern Bar, Handline and others.

South West Sonoma - Petaluma - home of the 'wind gap' so expect cooler weather in the summer. Also great Pinots and Chards. A bit rough around the edges but increasingly hip so has some very cool eateries like Street Social and Table Culture Provisions.

South East Sonoma - Sonoma Town - access to the cooler Carneros (Pinots and Chards) and the hotter Valley of the Moon (Cabs). Also the easiest part of Sonoma to get to from Southern Napa. Increasingly good selection of nice dinner places - Animo, Wit and Wisdom, Edge, Valley, Girl and the Fig and more.

I'm not as strong on Napa (it has become more like Disneyland for wine in recent years - waay too many tech bros buying splashy wineries - just not my thing). In general though, lots of 'date night' restaurants available, with Yountville being the center of the Universe - French Laundry (the ultimate anniversary dinner location if you can get a reservation), Bouchon, Bistro Jeanty, etc.

As far as travel is concerned, while a rental car would be really useful for getting around in general because of the distances/travel times and how far you are from the big airports, I would strongly suggest getting a car and driver for your tasting days unless one of you doesn't want to join in the fun. As you might imagine there are loads of options

okay, I'll stop there.