We cruised the South Pacific on Voyager in November 17 but without children.
The "train" is actually a road vehicle pulling a chain of open carriages through the streets to sightseeing spots. We stopped at a hotel for a cool drink and snack about halfway round. It's a good way to see the main sights and many photo opportunities. We left the tour in the town centre for a look around the market, which is easy walking distance back to the ship. I can imagine young children getting bored once the novelty wore off.
Enjoy your trip.
