I find it very difficult to control how much fat my teenage kids consume. Everything they like is loaded with the stuff. They don't listen to me about diet and heart disease. You are not alone in this.
Adolescents have a passion for taking parental advice as a sign of senility.
And dietary advice to prevent heart disease is particularly difficult for them to swallow since you are talking about something that may happen sometime in some very far distant future. One approach that might help, however, is to focus more on saturated fat and less on total fat intake. Yet, there is considerable evidence that it's a low intake of saturated fat, rather than total fat, that may lessen the danger. Allow a slight increase in fats derived from plant sources. Still, the purpose of the ACN recommendation is to provide flexibility, in the face of reality, and to enhance the palatability and acceptability of a more healthy diet for youngsters.