Most states exempt parents from such laws. For example Massachusetts law says
> For the purpose of this section the word ''furnish'' shall mean to knowingly or intentionally supply, give, or provide to or allow a person under 21 years of age except for the children and grandchildren of the person being charged to possess alcoholic beverages on premises or property owned or controlled by the person charged.
> For the purpose of this section the word ''furnish'' shall mean to knowingly or intentionally supply, give, or provide to or allow a person under 21 years of age except for the children and grandchildren of the person being charged to possess alcoholic beverages on premises or property owned or controlled by the person charged.
https://malegislature.gov/Laws/GeneralLaws/PartI/TitleXX/Cha...