Never been to Idlewild, but it's near the top of my list of things to do so cant help you there.
Best hotel deals near the park would be on Priceline. Look near the airport, you can get some really good deals, use Biddingfortravel.com to hone in on a good value. Ends up being like 20 mins from the park, but that's probably a good thing (park is in a somewhat run down area).
If Priceline isnt an option (dates not set in stone), I'd check the Motel 6's in the area, that is where I used to stay and they were always the cheapest in the area, before I saw the light and started using priceline almost exclusively

Favorite Wood Coasters: The Voyage, Ravine Flyer II, Thunderhead, Balder
Favorite Steel: Voltron Nevera, Steel Vengeance, Expedition GeForce, Olympia Looping
Parks visited: 232, Coasters Ridden: Steel: 894, Wood: 179, Total: 1073