I went to the Christmas Carol Train when it came to Union Station in Denver.
It opened at 9am, we got there at 9:30 and it was a 2 and a half hour wait.
It took us about 20 minutes to go through, with about a 10 min. sneak peak film in 3D at the end.
The train itself was pretty neat. I for sure expected more for that long of a wait. There were only a few items of Charles Dickens, mostly screens along the wall of the train cars showing about the movie. I'd say there were probably 6 train cars, and 2 or 3 of them were just filled with the machines that take your pic then put your face on 1 of 3 characters from the film.
I thought it was neat but for sure not worth the wait. So if you have small children I would consider arriving very early, like an hour or two, or at least that is what the people working the tour said we should have done.