IMO Kohler is not suitable for kids. It's more of a spa and foodie experience.

One possibility which is somewhat unique but a long drive is Macinac (spelling?) Island. It has a restored grand old hotel, no cars (think horse and buggy), sense of history, etc. However, I'm not sure how good it would be for modern recreational facilities like one would find in a big new resort.

Another unique experience would be to check out the facilities associated with some of the preserved Frank Lloyd Wright buildings. At least one of these in the midwest has been expanded into a small resort, but I don't remember where or any details. Of course, with children, you wouldn't expect to actually sleep in a FLW building, but rather some upscale lodge or newly-built "villa" on the grounds.

Someone suggested Pennsylvania. The Seven Springs Resort has greatly expanded since I was there many years ago, but it now claims to be luxury level. It might be worth checking.

Along the shore in MN north of Duluth, most of the resorts seem like tacky but there are a few that look nice. Sorry that I can't remember names. Probably about eleven hours from Chicago, so long drive, especially with kids in the car.

ADDED: Canoe Bay also is not suitable for children.