Sounds like a great event for your troop. Hope you are fortunate getting parents to drive, we scaled back all of our campouts and events to be within an hours drive as it is like pulling teeth to get parents to help out if the drive is any longer.
I am currently a scoutmaster and have had the RR merit badge as one of those I am registered as a councelou. Being SM, it is nearly impossible to find time to run any merit badges any more though. I did the RR merit badge back when I was an Assistant Scoutmaster, we took the scouts to the DRGW Burnam shops in Denver, North Yard and car shops, Colorado RR museum and caboose hobbies, had 15 boys (half the troop) take the badge.
We are having a backpacking trip in August on Boreas pass on the old South park line. I would like to try and find the time to use it as a basis for RR merit badge again if I can find the time. We are planning on stopping at the old Como Roundhouse and have breakfast at teh RR Depot B&B before heading up teh pass and leaving the road (former roadbed) for a hike in starting from around the Baker Tank.
Boreas Pass is one of the most scenic RR lines I have seen, marshall Pass also rates. We just took a family Bike trip last weekend in Silverthorne and came home via Boreas Pass, it is spectacular.