We've gone a couple of times for the July 4th holiday! It is a great time to visit! However, I would suggest avoiding the MK in the afternoon/evening of July 4th. It is very crowded, from what I understand. For our July 4th visits (in 1998 and 2000), both times we did the MK in the morning, and in the evening (after our nap/swim break), we headed to Epcot. They had a wonderful fireworks show after Illuminations in 2000 (in 1998, all fireworks were cancelled due to fires in the area). We had a great time - it is crowded, but we found if you went to the "early entry" park in the morning, and go to another park in the evening, we didn't run into much of a crowd at all! (Without EE, I would just suggest any park but MK)
Check out the Tea Party with Alice in Wonderland - my now 6 yr old has done it three times and loves it!!
Enjoy your stay!!!