My personal preference is the Swan. The rooms are slightly larger and, assuming you have requested two beds, the Swan has queen beds while the Dolphin only has doubles. The Swan is smaller, which I like. I think the Dolphin is just too big and can be a real zoo. True, if you stay at the Swan, some of the amenities are over at the Dolphin (i.e. the gym, Tubbi's Buffeteria, etc.), but that isn't really much of a walk to be any real inconvenience.
Last year was my first year as platinum and I had one stay at each property. Although I didn't get a suite either time, in both cases I was upgraded to balcony rooms overlooking Epcot. That said, for my upcoming Swan reservation in March, my reservation already shows an upgrade to a suite.
I'm not sure I would recommend a red eye, particularly with kids. The parks are tiring enough without starting out with a mediocre and shortened night of sleep on plane. I think you are better off arriving in the early evening, having a nice dinner at the Boardwalk and getting a good night sleep before taking on the parks full force the next day.