I agree with the previous poster. Use Priceline. We did that on our last trip to WDW and got the Marriott at the airport for $25 for our first night (arriving at 11:30 p.m.) and for our last night with an early morning departure the next day. It was a good, clean, convenient hotel. Of course you aren't guaranteed a specific hotel, but if you pick a 4 star in the airport area you should get something comparable.
Good luck!