Okay, I'll admit it. I took my son to a Thomas event a couple years ago at Strasburg. Even though I had been there many times during "Tourist Season", I had not seen such an onslought of money spending train fanantics. This was a good experience for grandparents to totally spoil their grandkids by riding the trains and buying up all kinds of Thomas trinkets.
They would run a train of 4-5 couches down the line a bit in between the regular trains, and those cars were absolutely stuffed ! I did some math and figured that over the course of the 3 day weekend, the could haul as many as 10,000 guests on these trains.
I'd think it would be better for the D&S to schedule this outside of Railfest, as the hardcore railfans will poo-poo Thomas and the fans that come see it.
And if it was possible for the C&TS to host him, they might be able to attact folks from Abq, Santa Fe, Pueblo, and the Springs for day trips. People that don't want to stay overnight and wouldn't normally think of riding the train might find this as a good introduction to the railroad. Just a thought.