You've probably spent a fair amount of time at the airport. If you're at SFO, there are some things that can keep your kids entertained.
#1 - the tram
If you have extra time, it's fun to ride (well, fun for the kids). And you get a totally different view of the airport. There are only 2 cars - so if you ride in the front car, you can get snag a seat (like the one above) for a forward-looking view of the ride. In the second car, you obviously get the rear view.
SFO has a certified museum - spread around the various terminals. We are usually flying out of United's terminal 3, and here's what we saw in February: televisions. The kids though the space-age and older TVs were quite funny.
At the end of that wing, near gate 87a, is the "kid spot." This is not the best picture (below) of it, but it's good for toddlers and other young kids. There's a tunnel-like caterpillar tube, a globe with soapy stuff in it that looks planetary, and a plasma wall with color that's activated by sound. It's supposed to help you explore weather concepts, but really it's a place for kids to play while you run over to Peet's across the way.
We also like visiting the various Ghirardelli stands and looking long enough for them to give us a free sample. You can buy squares by the piece (they do it by weight) but you're looking at about 75 cents a square. Just so you know.