I have to ask, why would you want to book one night only on the way in? Is there not room available at Club O that night? As otherwise, I would just get a taxi that night to take me to Club O, as opposed to messing with a one night reervation somewhere. If you stay somewhere else the night before, and then show up at Club O at, say 11 AM, if you go out for breakfast somewhere, you are probably still not going to be able to get into your room until 1, 2, or 3 PM anyway. Unless Club O doesn't have any space, I would just go there that night. If you wanted to stay a couple of days on the Dutch side, I might do that at the beginning, but I don't get staying one night somewhere.
As far as hotels in MAHO, which is what you asked for, I really don't know, but isn't the Sonesta only a/i?? If so, I think that would be an expensive choice that you wouldn't use the a/i facilities. And Royal Islander is the only other hotel in Maho, I think, and since it's timeshare, you might not be able to get a one night there in dead high season, and it probably would be pretty expensive. As far as the suggestions you have received so far, most of them probably wouldn't accept a one night stay in the dead of high season, unless booked at the last minute. I could almost guarantee you that Horny Toad would not. You best option of those mentioned for an inexpensive stay might be Mary's Boon, in one of their below grade rooms. For someplace that's close to the airport, I might suggest Alegria (...waiting for brickbats to come flying my way!! <img src="http://www.traveltalkonline.com/forums/images/graemlins/Laugh.gif" alt="" />) or Simpson Bay Suites, both of which are regular hotels, so you shouldn't have an issue with getting a one night reservation.
But if it were me, I'd just go to Club O that night. (And not for nothin', but I HATE that AA changed their late Miami flight to arrive SOOOO late in the winter! <img src="http://www.traveltalkonline.com/forums/images/graemlins/Mad.gif" alt="" /> Ridiculous!!)