My DH and I stayed at the Swan for one week in '06. We were very happy with this resort!
Main difference between the Swan and Dolphin is that they're owned by different chains (Westin and Sheraton respectively). Which probably means nothing to most, unless you have one of these hotel cards for usage points for upgrades, $ off of room rates, etc.
The Dolphin and Swan are next to each other, joined by the docking area for Disney trans to take you to the Boardwalk, MGM, or Epcot (WS side). This is so convenient! The Boardwalk and Epcot are also within walking distance. Both resorts also have pools (Swan has a lap pool too), restaurants, etc. And the Disney mini-golf is also next door.
We had great service, very nice rooms and REALLY comfortable beds! You guys will have a good time!!!