I went with my dad in 2019 Memorial Day weekend. I'm not sure if y'all have time but I loved Erin Hills and it's only 45 minutes outside of Milwaukee. We stayed in the third ward in Milwaukee and there's a decent amount of stuff to do. Went to the Milwaukee Ale House, Public Market, and the Harley Davidson museum.
I only played Whistling Straits at Kohler but depending on the wind, the lake won't come into play as much as you would think. Every par 3 is similar in that they sit on the edge of the lake with a steep drop off. TV doesn't do the 17th justice, it's a very intimidating shot. The 5th hole where Bryson took that ridiculous line was one of my favorites.
Not sure how long you're in Chicago but I could probably start a whole thread on things to do there. I'm not necessarily a huge art guy but the Art Institute of Chicago is awesome. It's in Millennium park near the bean.