How strenuous is this activity? Are there hills?

This is approximately a two hour  self pedaled   round trip excursion.  Railriding is a physical sport that does require some effort but most guests are up to the physical task.   However, all the pedals are free wheel.  Strong guests can help the less able guests if all agree to the arrangement. Yes, there are small undulations  along the route. This  is basically a flat, average 1/2 % grade change, route.