If you drive to the airport yourself, make sure to check out the coupon on the Buffalo Airport site.
I often use priceline bid your own price for a hotel for the night before. To check out what others have bid on hotels check out this site.
http://www.betterbidding.com/
Usually I end up with the Millenium. I've paid from $42 to 65 dollars for it through priceline. You can still take the shuttle and park there for a price. I think it was $7 a day or something. Call the hotel to find out for sure. The Hotel is about a 12 minute drive shuttle to the airport. The Millenium is fine for my family as they have a pool, are across from Olive Garden and beside the Walden Galleria mall (Can you say Cheesecake Factory?) However, they don't have breakfast included and they could really do with some updating. But we love being able to walk to the mall and have drinks with dinner without worrying about driving. After all our vacation has started even if we aren't in Disney yet.
I've also stayed at the Best Western. They are super close to the airport and their breakfast buffet starts at 4:30 and they have a make your own waffle machine (which is a huge selling point for my kids). Again the place needs updating but I usually get the room for under $100 and my hubby loves a free breakfast.