If your family members you will be with are supporting you and not drinking also: don't even mention drinking or making it the "elephant in the room". Make plans beforehand on some activities so there will be structure and not so much time to fill with "let's have a drink" or "i'm bored, wanna have a drink". have a routine to the days. i think if you have some reading that is inspirational to you to keep on keeping on. and also a vacation journal so that you can talk to yourself and let out any negative feelings or thoughts of being scared, awkwardness and the good stuff too. then you can read it later and see how things went - your true thoughts at the time. for every day that you don't drink and do other activities, send a postcard to yourself - something to look forward to when you get home. write positive things on them.