You are confusing the voting and drinking age for the age of consent. Today, in most states, the age of consent (to sexual intercourse) is 16. Very likely, the age of consent in 1960 Hawaii was 18. If you are referring to a girl's ability to pass on citizenship if the child is born in a foreign country, then that is a different issue from legal "adult" status.
I believe Joel Gilbert’s film says the age of consent in Hawaii in 1960 was 14.
Drinking age was set at the age of 21,in most states, but not all. Only later after the plea, that if someone was old enough to serve in the military at 18, they should be able to vote and drink, was it lowered. Until that time, parents were considered responsible for all acts by their minor children.
At one point the drinking age was 18. Students in high school could go home for lunch and bring back alcohol to the schools and share it with their underage friends. This was a nightmare for schools. Fortunately they later raised the drinking age back to 21, and in most cases closed campuses.