We've also made many summer trips, and this will be our third time going for the 4th of July! (My favorite time is the week AFTER Thanksgiving though!!)
As the other poster said, I think its important to have a plan. Use fastpass. We like to get up early and hit the parks; then go back for a nap/swim break. Then we go back in the early evening and stay as late as we wish. (Usually, the crowds have thinned out a lot as the day wears on).
If there are any "must do" restaurants, be sure to make your PSs as soon as possible.
Then - go and have a GREAT time!!! By the way, we'll be there July 2-10; maybe we'll see ya there!!!