We are taking our 11 year old grandaughter to SFO this summer for 3 days. I know it is not very long but the best we could do.

With this limited abount of time please let me know what things we must do. We are staying at the Marriott Courtyard at the Wharf using my Marriott points. We are flying so we will rent a car.

Have fun

I highly recommend taking her to the Exploratorium, the hands-on science and arts musuem. My kids loved it and so did we. (That is to say--it's not just for kids.)
If you are all in good physical condition, consider booking a visit to the Tactile Dome inside the Exploratorium as well. You have to walk and crawl through an enclosed space just using your sense of touch because it's completely dark inside. It was pretty neat and my kids LOVED it.
Check the Exploratorium website for more info.

I totally agree with longhorn55's suggestion of the Exploratorium and especially the Tactile Dome. My 12 year old loved it last year and went through twice. (I however freaked out a bit inside. The darkness got to me.)

We only stayed in SF for 2 days so didn't do much else. Breakfast at Dottie's True Blue one day and Sears another and dinner in North Beach (Rose Pistola).

I took my daughter to SF last year (at almost 11) and we had a fantastic time. If you click on my screen name, you should be able to find our trip report. We fit a ton of stuff into our 2 1/2 days, and she's looking forward to going back to take see all of the things we missed.

We always took our kids on walking adventures, which they loved. As adults now, they love sharing these view-laden walks with friends. Look for the book called Stairway Walks in San Francisco.

You will also be close to Hyde Street Pier. You can walk all over historic ships and a ferry.

Your grandaughter might enjoy walking across the Golden Gate Bridge (wear a jacket! It's windy!). Also take a ferry over to Sausalito, then walk along the waterfront to enjoy SF from a different perspective.
A walk through Chinatown is fun; eat at Hunan Homes on Jackson St.

Golden Gate Park is full of fun places, too.

If she's into this type of stuff, Alcatraz, though a bit touristy, is worth it.