We've had some difficulty finding a room block because there is a big medical conference happening the weekend of our wedding. We've been seeing hotels at the low end of $300 per night, and upwards of $900 per night when using a site like kayak.com or hotels.com . We have occasionally seen some good hotels (3 star) for under $200 per night, so we recommend checking online, and seeing if you can book something right away, even if you're not sure you're coming. You can usually cancel 72 hours, a few weeks, or a month ahead without a charge ( depending on the hotel). Coordinate with other family/friends if you'd like to all stay in the same hotel.
If you can't find a hotel in the city that is affordable, you might check out Air BnB, hotels near the airport (30 min drive, $35 Uber/Lyft), or try the Holiday Inn Express in Mill Valley (25 min drive, $30 Uber/Lyft) where Summer's family is from (right across the Golden Gate Bridge). Let us know if you need any help finding accommodations.