We were at OKW a week ago (checked in two weeks ago). We were driving down from NJ in our motorhome and were at the FL border early that Sunday morning. My wife called to find out how early we could possibly check in. She started to get the standard message of how we could check in and when our room was ready, etc. etc. When my wife explained we had the 35' motorhome and ... before she could even say another word, the person said "I understand, we do have rooms available right now, here's what we have, what would you like? When you arrive you'll be able to get right in and unload without the congestion." We were in our room at 11:30AM.
What I've learned, whether with check in or any other aspect, if you have good reasons, they will accommodate you as best they can under the circumstances.