We went last summer for the 4th, but not as DVC members yet.
It was really hot but as long as we had on hats (definitely a must) and left the parks for rest in the afternoon we were okay. Only stayed in the parks for the 3:00 MK parade one day, other then that we were out of the parks by 2:00.
It was crowded but as long as we were at the parks for rope drop we were able to accomplish a lot with the fast pass system.
Spent the 4th at AK, was not crowded at all. Then went to rest, swim, and headed to the MK to eat dinner and watch the fireworks. Be warned the MK will be packed. We ate and then worked our way back out of the park and watched the fireworks from were they launch the boats. We probably had the best viewing area there is and only about 10 other people with us. The majority of the fireworks actually came from the beaches across seven seas lagoon. Had a 360 degree view of fireworks. The only down side is that you can't see Tink fly, but beating everyone to the bus stop sure made up for that.
Have fun!
Lori