Hey,
Sounds like the girls haven't been out much so that they don't know what's out there...that being the case, here are my ideas.
Spend time listening to them. Play 20 questions or board games. The important thing is just to listen. Bring a newspaper, ask about events listed in the paper. Make a plan with them to explore SF. You might find they've not been to some of the tourist sites. Explore.
Just take a walk - in SF, start at the ferry building and walk all the way up the Embarcadero all the way to the GG bridge. You could begin to know more about the girls and their interests that way. There are so many neighborhoods close by to explore also, from Chinatown to North Beach.
If you find they like the outdoors, the Marin Headlands are beautiful. (The beach, light house...)
Walk some of the many college campuses we have in the Bay Area and ask about their dreams. Help them set goals. Work together to reach them. Talk with their teachers.
Half Moon Bay. Davenport, Santa Cruz are nice day trips. There is so much to see and do in the Bay Area. We are truly blessed. (Go the opposite direction, Sonoma. Or east...)
Go get ice cream....have tea in Chinatown...eat food that is different from what they are accustomed to.
Window Shop.
Take them to places (museums, concerts, bike riding, skating, Golden Gate Park...)and things you are passionate about as a starting point.
Most importantly, take the time to listen (slow and steady) and answer any question they may have about you honestly.
What a wonderful opportunity you have to get to know and make a difference in the life of two young women.