If you can, rent a lake-side house. That way, the family can go swimming without you having to pack up the car and going to the State Park beach. Get one with a dock as most of the shore line is rocky. Some rental houses will have kayaks or paddle boards for you to use.

Depending on your kids ages, you can rent Sea Doos/WaveRunners or boats (either pontoon or ski boat), with add-ons like tubes, skis, and/or wakeboards.

Hit the Honi Honi Bar at least once. It's next to Pizzeria Uno's. And make sure to hit Lakeside Creamery for desert.

There are some nice hikes up there - Swallows Falls is a good one.

Wisp Resort has the Mountain Coaster, which is cool. You can also take mountain bikes up the ski lift and ride down various trails (with differing difficulty levels). You can also just ride up the lift for a mountain top view and ride it back down.

At the top of the mountain (not associated with Wisp) is the Adventure Sports Center International, where you can go white water rafting in a man-made river/facility.

There are also some go carts and mini-golf places around.