I think you'll find that most of the Buffalo hotels have a "airport stay" rate which includes one night, breakfast, shuttle to and from the airport, and up to 2 weeks free parking. Just ask when booking... but do it now as they are filling up, especially if you're looking at a weekend. Most hotels are filled with shoppers.
I have only stayed at two hotels that had that package, so I'm not the best judge. I've stayed at Comfort Inn University, which is very basic but clean. I've also stayed at the Hampton Inn (airport... really Galleria) which was quite nice, and close to all the shopping. A bonus with both is that they had indoor pools if you want to partake before your trip.