Boardwalk is mostly dining and shopping. In the evenings, there are entertainers and carnival-type games, as well as street booths for things like hair wrapping and face painting. You can rent bikes and pedal-trollies (the kind where the whole family climbs in and then has to pedal in unison to make the thing move ... harder than it looks, but really hilarious to watch with some families!
) to get around, and there are a couple of game areas (most notably, inside the ESPN Club). You can see some of the fireworks from Boardwalk as well.
It's fun for kids, but probably not for a long time. Unless you're eating there or your kids are REALLY into sports and decide to camp out at the ESPN Club and watch the many screens, an hour or two will probably be long enough.