You'd think that the $200 the parents paid CO for the UM fee could have included the fee for DTV. On the other hand, do parents have a right to control what their kids watch? There are parental controls on the AVOD, but not DTV. And if some passenger is going to comp the DTV to the kids (to keep them quiet presumably), the parents really have no way to enforce a "no TV" rule, if that's the case.

By the way, if you are sending your kid somewhere alone, stored value VI/MC/AX cards are definitely the way to go. There are sites where you can order them embossed with the child's name and can track the spending.