I just called and did all of my ADRs for the 13th-20th. Got everything I wanted at the times I wanted. So urge you to call.
The CM was very, very helpful. This is my first trip to the World, so had a list of resturaunts my kids wanted to try but hazy on the exact times. The CM was very helpful in suggesting slightly different times for parades and fireworks!!
So....who knows if I made good choices, but we will roll with the punches when we get there.