Paul,
We designed Mt. Prospect CC (IL) 5 years ago to have a Family Putting Course. They have very much a "private club in the community vibe" with kids often riding their bikes to the course-makes me genuinely happy to see. Mt.P is a park district owned course, and worth seeing if you're nearby.
We also built one integrated into the Giant Green at Black Sheep back in 2000. The overall green was nearly 2 acres and included areas generally designated for; the "normal putting green", the 27th Green and the 19th Tees. The area shaped for the Putting Course was about 1 acre, but the Golf Staff (Kevin Healy) did a great job using the entire area for fun even though the Putting Course, it was typically maintained at about .25" to .50". The slopes were interesting, but the then Contractor shaped it in a hurry since it was literally the last thing done on the project and ended up dormant seeded and covered with Futera Blanket if I remember correctly.
Two years ago we (Esler Golf & Vintage Golf Construction) rebuilt the Putting Course at Black Sheep, and it is the only one in the Chicago Market that I'm aware of. I spent an enormous amount of time shaping and fretting over slopes and transitions. Even had the John Deere rep with our Super come out to make sure it was all mowable. It is now spectacular, google earth has it partially seeded, and the separate shortage area to the west is growingin in that aerial, late 2019.
We're in discussions with two wonderful old clubs/courses; at one to restore/replace a Putting Course that once existed, at the other to Build a new one incorporated into the 1st Tee Putting Green Complex.
I've heard of one other Chicago area club that is considering a Putting Course.