I would agree with David (60103) on this. Having two on each train makes for more fun, and for more "prototypical" operation. The group I operate with on occasion almost always runs two per train, in part for the social aspect... Also helps with regulars showing the ropes to guests, etc, etc.
If you are lucky enough to have a "crew lounge" area, set up a video or two, some snacks, etc for the crew that is not in the train room.
Andrew