I was down last year for the 4th. My suggestion is for you to go to MK on the 3rd and than plan on begin at DHS or EPCOT for the 4th. My understanding is that last year DHS debuted a new version of their fireworks for the 4th. EPCOT always has a tag at the end of Illuminations to celebrate the holiday.
If you do decide to be at MK on the 4th, like we did last year. Plan on showing up EARLY. Last year, MK opened at 8 instead of the usual 9. We were there at opening and spent most of the day at the park. As the time for the fireworks got closer, the park did close b/c of capacity issues and it got to the point that you couldn't move on Main Street. They were actually ushering guests backstage in order to accommodate the crowds on Main Street (not unheard of). We ended up watching the fireworks in Fantasyland right by Pooh. Once the fireworks ended, the crowds diminished greatly.
Either way, plan accordingly and be prepared to encounter HUGE crowds and long lines. :wave: