Drunk driving is most common between the age of 21-25. I say offer them the option - if you are going to be drinking then you will not get to drive until you are 26. And if you would rather drive then no drinking at all between that time period. If they break the rule then not only suspend their license but also, fine them and let them do some jail time. All of this is very important for them to learn the consequences of drinking and killing innocent people.
One of my friend's brother was killed in drunk driving while he was crossing the street. His mom went crazy after hearing the news and never came back to live a normal life again. She eventually died of a heartbreak. The son was only 19.