We have a ranch on the east side of town, but our westside go-to place for picnics is Calcareous. Their wines are wonderful and their tasting room is breathtaking. Their staff is friendly and always happy to share other local touring information or recommendations as to other interesting wineries to try.
This is also an incredible venue to hold an event. Their tasting room has glass walls that can be opened up, so it is essentially an open room with a roof, but they have a built in area right at the edge of their property, overlooking all of Paso, that would be perfect for a bride and groom to stand to pledge their eternal love to each other. They have an on-staff chef but other catering companies can be brought in. Our family held a birthday brunch there this year for 70 people, and it was a brilliantly sunny morning, the food delicious, and the venue could not be beat. They even have a bocci court, for those wishing to take on the challenge.
There are a few twisting roads to traverse in getting there, and it's never wise to drink and drive, but if you're considering an event there, it might be worthwhile to consider hiring the Grape Wrangler or one of the other wine shuttle touring companies to take your guests from the hotels to the winery. They're well versed in making rounds from the various hotels to a venue and back a few times, with graduated drop-off and pick-up times.
All in all, one of the most beautiful places in Paso and worth a visit. Enjoy!