We travel and peak times and myou famity has never seen a park opening. Mid-July, Christmas, Spring Break, 10+ sometimes 'insane' crowd levels and evenings are great! We sleep in, enjoy the pools, arrive about noon, schedule FP throughout the afternoon interspersed with shows and less popular attraction. By early evening, lines at character meets and kids' rides are low. Late evening hit the headliners again, fireworks, leave when they kick us out because it is amazingly easy to ride everything at the end of the day. Crash about midnight, sleep in the next day, no alarms, wake up whenever, do whatever we want until first FP about 1-2pm. Repeat for 7-10 days.
Down side is that afternoon storms tends to disrupt plans during the summer, but they thin out the crowds even more, and afterwards we often have 'anytime fp' to play with.
We have done this since our kids were toddlers, and it works great for us. SO much more relaxing, no struggles getting everyone going together or arguments about not wanting to leave.