The foremost thing before you start a conversation with your child is to check are you yourself following all the rules and regulations which you are about to discuss with your children. Young children adapts several qualities of their parents and if they see them drunk all time or using an excessive amount of alcohol on and often then how will you be able to make them realize the difference between good and better. First make your position such that they trust whatever you say and positively agrees to your point.
Start the topic of alcohol education with a friendly talk and keep the environment calm and cool so that the children do not take any negative impact from your harsh or rude behavior.
Clearly explain them the limit of alcohol intake and the best way to convince them is that you should also switch towards the similar intake amount or else they will never accept your rule until the one who made it is not following it.
Keep a moderate amount of alcohol bottles at home and if you have a sort of collection then keep them out of the reach of your children.
Openly and clearly explain them the scenarios to which they might lead if they start having excessive amount of alcohol. According to medical experts young people take more time than adults to process alcohol so the best solution is to drink less and try making it once a week.