Visit a science museum! Click this link for a list of fun science museums around the Bay Area. If you have a library card, you can visit some for FREE through the Discover & Go program. If you are receiving food assistance (SNAP benefits), you can also visit some for FREE through the Museums for All program.
Spend time outdoors! You can go to a county park, a state park, or even a national park. Fourth-grade students and their families can visit state parks and national parks for FREE. If you have a library card, you can borrow a pass for county parks and state parks.
Do citizen science! Citizen science is where everyday people contribute to real science research. Two of my favorite websites are SciStarter and Zooniverse.