Great Wolf Lodge Niagara is a fun, family-friendly indoor water park with 2 million liters worth of slides, pools, falls and activity centres. Right now they're running a 48-hour sale with family suites starting at $159.99. Just use coupon code R48HOUR at checkout to get the lowest possible price. Keep in mind that the cost of the room includes four passes for the water park (and extra passes can be added for about $40 each).
Rates vary according to date, with weekends being the most expensive and Monday-Wednesday being the very cheapest. You can get a look at how the rates play out in this post from forum poster JonJubeTube.
The discount is valid on stays now through July 12, 2012 and the sale ends May 10, 2012 at 11 AM EDT.