The above answer is perfect.
There is absolutely ZERO need to call ahead. There wouldn't even be any way for Disney to note that on your reservation, but more importantly, there would be no reason for it.
As long as you show up by 6 a.m. the following day, you'll have your room. It may be new and different for you to show up to a hotel late at night, but at Disney it's just another day at the office, happens hundreds and hundreds of times every day of the year.