Firstly congratualtions on the anniversary.....
I went to San Fran 2 years ago,absolutely loved it. I am not sure how active you are but if you could handly a gentle bike ride I would REALLY recommend hiring some bikes from near Pier 39 (make sure you stop to look @ the sea lions) but they do smell really bad, and like JimJools says it's horrendously tacky and expensive on the pier, so if your hungry eat/drink elsewhere. Once you are on your bike you can follow the flat riverside path, maybe stopping at the edge of the doc and sing yourselfs "sitting on the doc of the bay" (inspired by that very doc) and then cycle over the golden gate bridge (an experience I will never forget), once you get ver the bridge you cycle down hill all the way to Sausalito, have a mooch about this gorgeous little town and then hop on the boat back to pier 39, passing Alcatraz on your way.