Such a program might produce gross revenue of $800/day from these "cab rides" (say @ $200 a pop for a 2-hr stint at the throttle). Subtract from that the wages/payroll taxes of the engine crew, depreciation of the engines, routine labor costs in servicing them, increased liability ins. premiums, coal, mgmt. time, etc., and you get net profit for your effort. I don't know, but I suspect its a deal that might make sense only for a small, volunteer-staffed operation that doesn't depend on its power for daily operations. I'm not sure that it would materially add to your bottom line at an operation such as the C&TS. Might even be a net loss.
For the time and effort to set up such a program, you could probably invest it better in increased marketing. Another 50 adult riders grosses you $2,000/day for roughly the same cost. I'd be interested in the thoughts of the former CMOs that hang out here.
On the other hand, Bob's probably right about the waiting line.