I tried use iTunes voucher but I am not sure if it will charge my dad. How do I know?
As long as the app's price does not exceed the amount of money on your iTunes Balance, and you actually pay with the gift card.
If the Apple ID belongs to you, you will get the notification. If it belongs to your father, however, then he will get it. It all depends on who owns the e-mail address associated with the Apple ID you are trying to use.