We were just in SF in December with my (then) 6,5 year old and 5-yo twins. They liked watching the sea lions at Pier 39, and just playing around on the Pier. Cable Car ride is a must...they would have done several times if possible. Walking down Lombard street (maybe not so interesting for your 10-yo?). We went to the Ferry Building and wandered around, and there were some fun food stores (one of my kids is gluten-free, and there's a gluten free bakery in there!). There is a great playground just across the street, adjacent to the big shopping area at Embarcadero Center. My kids enjoyed the spiral escalators at Nordstrom...but they aren't used to escalators much at all where we live (European countryside), so YMMV. And just walking the streets... especially when they could run up or down the giant hills, was a joy for them.