The idea is to make it illegal to accept money from suicide bombing. Whenever there is a successful suicide bombing, make the parents cough up money you know they are getting, or else put them in jail for a few years. No wannabes. There are enough successful suicide bombers whose family you can go after.
Many countries have laws that deny people the proceeds of criminal activities, even if you are not the one who did the foul deeds. (Mostly directed against money laundering.) Why shouldn't there be a law against receiving money for murder committed by someone else?
Cheers,
Ben