That's cool. Sorry, I don't know anything about the club. Back in the late 80's I ran my KX250 on that frozen lake (studded tires). I also drove my 57 VW out there in the winter. Ah, the good old days........
You may have to make a road trip to Medicine Lake, or West Minneapolis area and ask around. We have a Medicine Lake out here in Washinton also near where my father grew up.
I have a friend from ML. He's still in the area, so I sent this thread to him to see if he knew any oldtimers who would know about this.