I would say the Swan for a few reasons. First the health club the older teens would like that as well as the game room. Then there is the issue of the queen, more room for growing boys. Then the fact that you are within walking distance of two parks, and the Entertainment complex at the Boardwalk. JMHO...the kids would be happier in the middle of all the action. You 8 yr old will love the pool and the game room too. And stop at the soda fountain at the Dolphin, the waiters and waitresses dance to 50's music once an hour, and they have great shakes and sundaes!
Oh and you have the Disney Card, you get 20% off at all the restaurants at the Swan and Dolphin. The kids can charge back to the room anything at either hotel, but not the parks, they do deliever purchases though.