We'll be there for 4th of July too! This is our third trip to Disney for July 4th, and we really don't find it all that bad!
Any time we go in the summer, we always get up early, then take a nap/swim break. Then go back in the early evening and stay as late as we want. Definitely use fastpass!!!
We've always been able to see everything we wanted, and ride many of the kids favorites over and over!! We've been to MK on the morning of the 4th, then switched over to another park in the evening. MK wasn't that crowded (but we left around lunch time).
We'll be at Epcot this year; and my DD is looking forward to making her mask!
Relax and enjoy!!!!! See ya there!