Bitcoin is like cash, if you're worried that your kid may do drugs, don't give them any cash or bitcoins, and let them get a job and don't let them mine coins. Or you can just talk to them, with some graphic stories and have them spend a day with a crackhead, that should work way better then the usual 'drugs are bad' spiel.
Yea, not all drugs are good - some of them are GREAT! Kids should understand that