Baligh person is no more a child in Islam. Once the child reaches the Bolough, he/she is no more a child even if the society calls them children. Baligh person has the responsibility to perform every obligatory act or worship according to his abilities. Baligh young person is responsible to do Amr bil Ma'roof and Naahi 'Anil Munkar according to his knowledge and abilities and the possibility of effect.
Dealing with parents must be with full respect even if they do what you think it wrong. You must avoid any word or behaviour which can cause hurting their feelings. Hurting the feelings of your parents or any of them is a major sin.