I would second the car rental from the airport and a drive to Niagara-on-the-lake. A leisurely day with a stop at a winery or two with a nice lunch is a great way to spend a day.

Search the Hilton forum for info on the choices on the Canadian side. If you rent the car park in the Fallsview Casino garage and get a players card. That will give you free parking for your stay. The buffet at the Fallsview is also good for a buffet.