I've been out sledding at -25 to -30° . You really need to be careful. You absolutely need a real windshield, not a low racer one, and as you mentioned you have to be so careful about any wind leaks or exposed skin. I recall the few of us brave souls that were riding that night. The show was solid and no fluff at all on the lake, you could actually see snow forming from the exhaust of the sleds. It was crazy.
I don't recall the place my wife and I stayed at in Munising years ago, but it was right on the trail, urban style sledding, but you could easily get out of town in a minute, and there was a rental place within walking distance of the hotel. It was right on the main drag.
Christmas is a nice place and so is Munising. Several places to stay in Munising but not much choice in Christmas. Just west of Christmas is where you really have to be careful if there is lake effect snow. It gets so bad you can't see more than 2 feet and some times less. Snowmobiling in the cold; make sure you have good windproof suits and warm long johns. We used to go out when zero or below and had fun doing it. I don't do that today though.
I haven't snowmobiled in a couple of decades. Mid 90's was the last time. I couldn't have given any current advice. But I would like to add...…. All the trails lead to bars.
Well, she gave him an ultimatum...pick one...this trip, or the reloading setup he's been eyeing....not both. He's getting a heck of a deal on some reloading equipment, unable to pass it up. I've gotten used to this type of thing over the years being almost perpetually single with married friends...nothing is solid until the significant other signs off on it.