Our family has visited the world twice now, and here is what I suggest.
Get up... early.
You're staying on property so there are buses starting I believe either an hour or 90 minutes before the park opens. Get there early, get a fastpass, and do whatever you want to do. The parks opens usually with regular hours 9-9. There's all Extra Magic Hours for hotel residents. Use these less-crowded times to your advantage.
So, now you've been at the Magic Kingdom (just for an example) since 9AM. You've noticed that the crowds are building up. You have a fastpass but most of the other lines are long. What do you do? (Since you asked me.) Go have lunch, use your fastpass, then go to the Animal Kingdom or Hollywood Studios, which are less crowded, thrill rides set aside. Now, it may be around 3 or 4pm. Watch the parade and go home. Take a nap, go swimming, and then feeling refreshed, before you leave, get a priority seating to maybe a 7pm dinner. Now, you're back at the park, meal all set up. Have a nice evening watching the Main Street Electrical Parade or Fantasmic and then the fireworks. A great way to end a magical day.
I wish you luck on your trip!
