Lin, that's really neat! My dad was born in 1941 and his siblings were all younger. Their mom used to drive them, and as many neighborhood kids as she could fit in the car, from Chicago to swim at Miller Beach. The they moved to Gary and then Miller. My dad went to Horace Mann. If your dad is around that age, if he ever heard of the weird guy living all alone on the Burns Harbor beach in the abandoned houses (a vacation cottage area) that were going to become the steel mill, that was my dad!
I think your relatives' house would have been by Wells St beach, which still has the concession stand. It's too bad your family doesn't still have the place. Some of the beachside houses (or inland a little) are rented out on Airbnb if you ever want a similar beach vacation!