Took the Little Monkey to the NYPD Museum. A whole floor dedicated to 9/11, which we didn't let him see much of. We'll have to figure out the best way to explain it to him, as we live about a block and a half from the site of the Twin Towers. But today was not the day.
Otherwise, he loved the museum. Not necessarily worth a trip if you're new to NYC, but a good stop if you're around the Seaport and need to kill some time.