He is pretty much spot on I think. A few things I'd like to add though would be to disregard his SLC nightlife opinion. There is plenty to do in SLC, if your 21 anyways; however, if it's a ski trip revolving around good snow, you probably wont be doing a ton of partying.
If I were you I would wait til a few days before the trip and keep checking weather. Both mountains kind of suck without new snow. Jackson does have a park, but Alta has many resorts close by with parks too. And if you have a friend living in Jackson, having a tour guide there will give you the most amazing access to crazy shit everywhere. But i wouldn't venture too far out of the gates without knowing what you are getting into.