Have you looked at Rammekins in Sonoma? They have a guest house and its walking distance to where you'd have a reception. Most of the wineries in the area are pricey but I bet with enough looking you could find something fairly reasonable.
I got married at Buena Vista Winery (one of the oldest wineries in California) in Sonoma. I did a lot of research on outdoor venues in the area to fit over 150+ guests that didn't break the bank and felt secluded and romantic. I would absolutely recommend this place. I'm a Napa native with a lot of guests who have attended weddings in the Valleys. My parents and I are continually told this was the most beautiful wedding and venue they had ever been to. Good luck! Tell us where you choose.
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