Just a note. You might find it faster to not use the boat to get to Epcot. If you use the boat, you will make stops at the Yacht/Beach Club and then the Boardwalk before you get to Epcot. It's not that long of a walk/wheel from the Swan to Epcot.
For MGM, the boat will be the easiest. The Swan/Dolphin is the last stop before MGM and the first stop on the way back. You can also use the walkway from the Boardwalk was well. That's a smooth ride for an ECV.