As I recall, the IL Railroad Museum (near Chicago) pulled in something like 20,000 people over the course of its two Thomas weekends - raising huge amounts of money for the museum. Live-steam 0-6-0 Thomas here - very cool, btw, and a spittin' image of the 'real' thing.
We finally took our kids to one of the weekends, and were overwhelmed - tents, food and massive crowds. Despite numerous trips over the years, we had never seen the museum this full, and after the Thomas photos & ride, most of those people toured the rest of the grounds, and rode the many other operating trains.
I really can't think of a better promotional device for rail museums at this time. If Thomas pulls people out and aquaints them w/your railroad, then I'm all for it. This could be a great way to get folks to the C&TS (if they did it), who may never have considered making the trip. Once there - they may come back for normal weekend rides, or spark life-long interest in the kids attending. I say do it!