... the safety and privacy of the user must be the foremost design principle at all times. If you find yourself straying from this, it’s time to do a hard reset and think about either achieving your growth goals another way, or deciding to abandon the project as a money making concern.

This is obvious enough if you’re building ethically, but children should never directly spend their parent’s money, so design your app to enforce this. If you have in app purchases, require proof that it is the adult making the purchase decision.