This really sounds like something that should be solved in parenting and
not code.
I fully agree to that, as dad of now almost adult kids, espacially if it's bed time ...
If these kids are so little, why do they watch TV at all w/o parental advice and why could there be a channel underneath showing something what the little ones shouldn't watch?
But kids are kids, doing whatever come to their minds, they can't be controlled all times. What may be sufficient is to implement a kind of PIN control, like on commercial receivers. A function where to set a white list of channels which can be watched w/o PIN and the list is then valid for recordings, too, where the source channel is also stored. But bed time is still human responsibility ... ;-)
=== Kind regards fnu