they arnt the same, and never have been. Non vollentry is exactly what you are doing for your children, ie making the decision FOR them. Now there are 2 more terms i can add which further prove the point "active" and "passive"
For instance a pt who has terminal cancer can chose to have no treatment (passive vollentry euthasia), can be mentally incapacitated or a child to young to make the decision and the parent, gardian, Medical agent ect makes the decision (passive non-vollentry euthasia) or can be kicking and screaming and bitting the doctor for refusing to treat them (passive INvollentry euthasia). Then we look at the active where the pt choses to die (active vollentry euthasia), where the pt is to young or incapacitated to make the choice (Non-vollentry euthasia) or where you stab the person to death for there inhertance (INvollentary euthasia, murder).
The fact that you dont know the correct termology isnt my problem, its your own