Hola! Besides the one day West Yellowstone Tour, any suggestions for another no-ski day?
Mind you, something to keep a 15 y/o interested....
Bobsledding in Park City. Ice skating, movies, bowling, hot springs, shopping, snowmobiling, ice fishing, snow shoeing and tubing/sledding are a few that come to mind, but it really depends on what you guys are into and where exactly you will be.
There is another topic here someone else talking about snowmobiling at Jackson Hole...
You might find some good info here about JHMR area
If he likes dinosaurs, the Museum of the Rockies has some neat stuff not found elsewhere. MT is full of fossils. Also has a planetarium.
Look up Homestead Crater in Midway, UT. Haven't been there but seems pretty unique.
Besides a trip into Yellowstone, which will require a full day for a snowmobile tour and reasonably several days and thousands of dollars, you can go dog sledding in Hoback Canyon (close to Jackson) or take the sleigh ride on the elk refuge during feeding time. Both are very cool, and the latter will have literally thousands of elk up close and personal.
You could also go cross country skiing in Grand Teton National Park. I've not done it for more than 30 years, but there's lots of flat terrain around Jenny Lake and it is spectacularly beautiful.
Or spend a night at the Yurt in Rock Springs Bowl (if it is still operating...).
20 miles east +/- from Park City off of US 40 is Heber City. Just south of there is Midway, nice little bedroom community for PC. When the billionaires moved in they pushed the millionaires over here.) There are are several rental places there that offer quad all terrain vehicles and you can ride the Wasatch State Park trail system. Could be fun if the snow is not too deep. Somebody probably rents snow mobiles there too, just never looked.
There is a very unique hot springs there too on the property of a resort called the Heritage? Very cool place even have year round scuba diving there.
The Olympic Training Center also has the bob sled rides, that is a RUSH. Zip lines and a mountain coaster thing. The Canyons had the killer zip line though.
Yellowstone is where I would take my kids to snow mobile though.