We just got back from a delightful week with our kids (14 and 12). SFO's a high-priced hotel town! We bargained hard for a suite deal at the Hyatt at the Embarcadero. The location was great--I encourage you to find accommodations no farther than 2 blocks from a BART subway stop or muni bus/street car/cable car stop.

For a 10-day stay, I'd Google for "San Francisco vacation rental" and go in search of a short term apt. rental. Also, check out the B&B/Inns section of tripadvisor.com for ideas. Don't forget, if you go through Priceline, they can't guarantee bedding for more than 2, so you must place a multi-room bid that will fully sleep your group.

If any in your bunch are 12+, the Segway tour was a huge hit with my husband and son! http://www.sfelectrictour.com/ I don't know if it's offered, but a 2-day pass to the Exploratorium would be ideal. Y'all will spend many happy hours there. The Tactile Dome (must reserve admission) is definitely worth the time/added expense. http://www.exploratorium.edu/ Spending a very long Saturday morning at the Farmer's Market is a "must do" activity.

Happy planning! What a wonderful opportunity for you and your grandchildren....

Diana Ball near Houston, TX