I grew up in the area, so I have a few tips:
Take a canoe ride, go fishing, go hunting, rent a cabin, climb the firetower and seneca point, go hiking, go see the huge old trees and the tallest tree in PA and the tallest White Pine in the the northeast called the "Longfellow Pine" (183 feet tall)
http://www.pabigtrees.com/, enjoy a picnic, ride the go carts, go horseback riding, ride some waterslides, shop at the numerous gift shops, see the huge whitetail deer at the Double Diamond Deer Ranch, get ice cream on river road, go swimming at the pool, eat at the classy clarion river lodge, go for a bike ride on river road, check out the "Mysterious Maze" at Jessie's Dream Park, go to the flea market in Leeper, get a burger and a beer at the Trails End Restaurant, Check out the Farmer's Inn in Siegel for a small zoo, driving range, petting zoo, restaurant, mini golf, and gift shop, enjoy climbing on the "Beartown Rocks" near Clear Creek State park (not far).
Many of these activities are dependent on the time of year, so plan accordingly.