To be fair, targeting kids is a viable solution, though I think they should start with younger children.

For example, teaching young school kids the dangers of not wearing seatbelts will encourage them to ask their parents to strap them in, and then perhaps the parents will think about doing it themselves as well.

I think they did this in the UK at the same time as running the clunk-click adverts.

There's also the argument of "you can't teach an old dog new tricks". Trying to convince the older drivers who are established in their ways that they should start buckling up would be very hard. Easier to convince the young ones I think.