Earlier quoted context omitted.
COPPA is fucking stupid legislation, but Google should at least provide a "parental consent" mechanism.
A parent can't 'over-rule' a federal law. "Hey Mr Food-N-Liquor owner, I give you consent for you to sell my 18 year old alcohol" etc
For example, section 4301.69 of the Ohio Revised Code states "Except as otherwise provided in this chapter, no person shall sell beer or intoxicating liquor to an underage person...unless the underage person is supervised by a parent, ..." (Quote abbreviated for brevity, but the elided portion doesn't change the meaning)