We have gone the last two years, and have found it best to stay away from the MK! Epcot does add extra fireworks, and I have heard that MGM does the same to keep the massive crowds down at MK. They even close down all transportation to and from the MK about 20 minutes before the start. You might want to try this; we head over to the Poly about an hour before, get a snack, then watch them from the beach. It is a great view, not nearly as crowded, and is easy to get out afterwards. We will be there again this year, and there is no better way to enjoy the 4th!
Laura