TX Steve,
I grew up in Atlanta and my parents have a place in Odgen so we fly between ATL and SLC all the time. I would warn you very heavily on the dates you mentioned. ATL, DFW, and SLC are all hubs for DL and the loads can be crazy. Weekends are also pretty bad and its ski season and christmas. Bad combination. Since there are 4 of you I would not get my hopes up of staying together. If you can get out to SLC, getting back should not be a problem if you are willing to travel on Christmas day. The 25th is the least travelled day of the year. Just start checking flights around the end of November and talk to the employee who gave the passes to you about creative alternate routings if the non-stops look bad. Again...the weekend before Christmas will be very tight...keep this in mind.