Noon is usually the grace period for everyone. I'd say they'll give you until 2pm if you call that morning and ask. I did this at another hotel and think it's standard practice. You call the front desk the morning of your check out and let them know.
I was at the HRH this year, and a couple was at the pool, saying they had a flight to catch in a couple hours. It was about noon, so they probably called and asked.
They want your money. You'll end up tipping the bell hop, and spending more money in the parks, so I don't think it will be a problem.