In case you are having trouble finding the train ride in the area, here it is
https://www.alpenglowadventurestours.com/
the most historic ride appears to be the Georgetown loop https://en.wikipedia.org/wiki/Georgetown,_Breckenridge_and_Leadville_Railway

To the south, a bit further,
https://www.leadville-train.com/

Back east towards Denver is the Colorado railroad museum
https://coloradorailroadmuseum.org/

It is also quite possible that they meant this https://www.royalgorgeroute.com/, which is a further distance to the south.

or maybe this?
https://www.royalgorgeroute.com/santa-express-train/
I suspect that is a discarded link.

The replacement for the Santa Express is in New Jersey.
https://the-santa-express.com/about/

But I think the 12 hour Zephyr in Alpenglow is the closest thing to a secret Santa train.

To the east in Colorado Springs, Pike's Peak train
https://www.cograilway.com/

To the south
Cumbres and Toltec scenic railroad
https://cumbrestoltec.com/about-us-2/cumbres-toltec-history/


Even futher to the west
https://www.rockymountaineer.com/about-us


I took the bottom of the BreckConnect Gondola (not the ski lift) to the Breckenridge Fun Park and did some of the things here
https://www.breckenridge.com/explore-the-resort/activities-and-events/summer-activities.aspx
You need to take the chairlift up to take the coaster down. 

The chairlift is about a foot and a half off of the ground.

Some more stuff to do in Breckenridge
https://www.breckheritage.com/home

I also ate at the Mountain Top Cookie Shop.

I went to a wedding shower (not bachelor's party!) for a wedding while I was there too.  The Chrysler Town and Country was much bigger than an Odyssey or Sienna. 


Another past time near Breckenridge is white water rafting.  The easiest trip is described here, along with lessons
https://www.coloradorafting.net/destinations/breckenridge-rafting/#filter/64

The difficulty on the lessons is 7+ which I suppose is a reference to your age,
with the Kremmling journey having a difficulty of 2+ I suppose you don't need lessons for it.

You may ask, what're the best places to stay.  With the split between ski lift and gondola it's a little hard to say.  I can't find a 4 star hotel that's on the northwest side of town that is at the bottom of the gondola.  I say try asking Breckenridge Grand Vacations or Breckenridge Resort Managers, both of which are in the same mall.

If you want a rental home, though, Highwoods at Shock Hill are close and not too expensive.  I stayed a ways out. 

I think the train ride I was looking for is https://www.strasburgrailroad.com/christmas-train/ to the east of Denver.  Supposedly an hour and a half out.