How does the Junior travelcard work?
You simply need to take it along while traveling with the pass or ticket for yourself. That's all you need to enjoy free traveling for your children.
On board the train
Once you're on board, you will need to present your rail pass or ticket and the Junior travelcard to the ticket controllers upon request. The controller may want to check your passport as well, to make sure you're the owner of the presented pass and the parent of the children.