What law are they above?
Mummy and daddy click the "yes please store my credit card details and use them for app purchases"
Then hand over tablet, with saved details in them and are surprised that little kiddy clicks yes when they get the offer of an extra life?
My kids have their own tablet, no card details stored (the wifi is not even enabled) and when they run out of lives on Candy crush, Frozen or whatever, then that's it.
They accept it and it's a great way of limiting time on the device.
If they use my phone, again no details are stored.
Is that bloody hard to put in the details or a password each time you want to buy something? If you need to top up every 10 minutes, you either need to give up, or stop buying freemium games.