Alex, there is a small steam railroad in Lincoln NH where you will be at Loon Mountain. I don't know if you knew about this. Check it out. Looking around with google I see what looks like steam and some other images that appear to be diesel.
I found details on the Hobo Railroad at Lincoln which I hope to ride on.
It appears there is also another shortline in the Loon Mountain area which steams a small German wood burning locomotive.