If they're travelling in the South-East, they could get a Network Railcard which gives 4 adults (ie 16+) a third off, splitting the cost of the railcard between them. The SE network includes the I. of Wight Ferry. If going beyond the SE they could get Young Person's Railcards. They'd need one each but there are discount codes of 10-20% on the internet if you look around or if they already have a student card. Another idea is if they haven't chosen a destination they might be able to find cheap ideas on train websites. For example, last week Greater Anglia was offering ?7 to Cambridge, and Virgin had another of its sales on recently.