Pier 39 is a really hard area to put in a category. It has restaurants, shops, street performers, movie theaters, and more. My younger sister was once traumatized by a mime who decided she was his "volunteer" in a performance.
Kids will enjoy the old fashioned carousel and seeing the sea lions at the famous K Dock. (You can also check them out at the Sea Lion Cafe--see separate journal).
The area is wonderful for people-watching and just walking around, taking it all in. There are tons of t-shirt/souvenir shops, an aquarium, and street vendors. This is a great area to take pictures, with the backdrop of the Golden Gate bridge and the bay.
There is parking available in the Pier 39 garage (across from the entrance). Pier 39, slightly more family friendly than Fisherman's Wharf, is located 2 blocks east of the wharf.