Permanently deleting apps

I purchased a new phone for myself and gave my old iPhone 5c (8.4 IOS) to my son since I no longer needed it. The problem is I'm trying to prevent him from using apps like Instagram, Vine, etc. and even though I have went on iTunes and hid them all, in addition to enabling Parental Restrictions, I am still able to download them back onto the phone, if I wanted. How can I permanently delete these apps? Thanks.