Thursday will be moderate and slightly busy. Friday will be slightly busy right away since many seniors will have graduated and they will show at park opening for the whole day, it will get worse as the day goes on and be very busy from about 5 to 10:30. Saturday will just be busy.
Make good use of the early hours each day. Use FastPass. The 4th is the night to have a long slow dinner. Try to watch Fireworks and Fantasmic on the 3rd, and WoC on the 5th.
The Grads aren't awful for the most part but small groups of teens all over the place. Sometimes noisy, sometimes cutting in lines. The main thing do is make it crowded, especially on the big attractions, they aren't riding Winnie the Pooh or the Mark Twain, Tower of Terror and Splash Mountain is what they want.