How long have they been camping? What kinds of things are you doing together on trips as a family? I really do hope you are not just sitting around. Camping is as much about them as it is you.
Since our daughter was old enough to ask for things we included her in our trip plans. She always got to pick things to do. She started camping with us in a tent at the age of 1. She's 30 and married now but still loves camping, and still looks for times to camp with us.
So have family meetings to plan trips. find out what there is to do in the area and let the kids pick things. Do those things, even if you hate the ideas.
Here's some ideas, camp at or near theme parks. You are not far from Cedar Point, what kid (or adult) doesn't love Cedar Point! And you can camp on site, and get early admission. We really got sick of theme parks by the time our daughter was a preteen, but indulged her until she got done with tech school. So yes, we got to hate going to those places. but we don't regret a minute of it.
You don't live far from the Red River Gorge in Kentucky. Camp there or nearby and spend some time hiking in those hills. There are more natural arches in the Red River Gorge than in Arches National Park in Utah. It's just that they are in a forest. It's amazing there! You can hire guides or go zip lining. Just being around some of the people that are really into that stuff can get any teen interested in being outdoors. There are lot of other really cool things to see in KY, caves, horse ranches, in Lexington there is the Kentucky Horse Park.
Don't be averse to drive to a nearby town and see a movie, especially if the weather keeps you from being outdoors. And yes, many small towns have "real" movie theaters with Dolby sound.
Do any of you bike? Wisconsin is among the best states to go biking in. We have lots of old railroad grades that are converted to trails. Does IN have anything similar? Even if you just rent for a day, it's well worth it.
And if they are really hooked on Internet and gaming, indulge their desire and take them to an Internet cafe for a couple of hours here and there. That will validate that you care about their interests enough to include it on a trip.