If the answer above is None it means there is no specific mention in the legislation, but you still need to ask local law enforcement before drinking in Samoa.
Selling or serving alcohol to a person under the age of 21 years is punishable with a three hundred dollar fine, imprisonment for nine months, or both. does not apply to a licensee of a food and beverage license provided that the person under the age of 21 years is under the supervision of an attending parent.
You can find more legal details and links here:
Wikipedia Legal Drinking Page