MarvG - the member who asked this question - selected this as the best answer posted by another Education.com member.
from a fellow member
Hi, Good for you for planning ahead for your summer vacation!
When my brother took his wife and two young kids on a road trip across the United States a few years ago, their first destination was San Francisco. They drove up from Southern California, and stayed at a hotel near Pier 39. While they really enjoyed the many entertainment options at Pier 39, including the Aquarium of the Bay (http://www.aquariumofthebay.org/ ), the feedback he shared with me was that there was a lot of traffic along the Embarcadero, and he would probably have his family stay outside the city next time and take the BART subway into the city to go to museums and other tourist attractions. Other feedback: it can be cold and windy in San Francisco during the summer, so dress in layers.
If your kids are young (under five), there's a place across the bay in Berkeley (that you can get to really easily via BART - downtown Berkeley stop) that I highly recommend. It's a play-based learning museum called Habitot Children's Museum: http://www.habitot.org/index2.htm
Our daughter's favorite activities at Habitot were making art on the painting wall in the art room, and getting wet at the water play stations in the back (she also enjoyed a wind and kite display they had when we went). It's very affordable and truly enjoyable.
There are lots of great places for kids in the SF Bay Area. The Exploratorium at the Palace of Fine Arts teaches kids about physics and science. The Bay Area Kids Museum across the Golden Gate Bridge in Sausalito is lots of fun with arts and crafts and lots of play areas. Alactraz is always cool for kids because it includes a boat trip as well as a tour of the island and old prison.