Not really, we are tucked away in the Redwoods! If you'd like to spend time in the city I would suggest spending time there before or after the wedding weekend.
If you want to visit other areas of Sonoma or Napa County definitely! There are little to no taxis, uber, etc. There are plenty of wine tour companies that can take you wine tasting.
We have experienced a hot April in the 80s and also cooler in the 70s. It will always get cooler at night and it will be an outdoor event!