Welcome both of you to SR,
My father-in-law was an alcoholic and when my sister-in-law (his only daughter) was getting married, she decided that she didnt want him to be there on the day as she felt it would be too difficult and just spoil her wonderful day. She had her eldest brother give her away. It was a happy occasion, despite this.
She went on to have a continued relationship with her dad (till he died years later of alcohol related desease), choosing, for her own health and happiness, when to catch up with him and when not.
Many alcoholics really need to 'feel' the consequences of their drinking and actions to stand a chance of changing their thinking and getting sober. Unfortunately even the consequence of not giving his daughter away at her wedding wasnt enough to make a difference to my FIL way of thinking. My father-in-law drank for all his life, was single for most of it and missed out on many family occasions due to his drinking. It is very sad - but it is what it is.
I have no doubt that telling your dad that he is not welcome to attend your graduation ceremony will hurt him tremendously, but that would be a direct consequence of him continuing to drink alcohol.
Pelican gave you the 'Al-anon' saying we like to use with our alcoholics and also generally in life - Say what you mean, mean what you say, but don't say it mean.
Al-anon by the way is similar to AA but is for family and friends of alcoholics and it really does help. Could both of you and perhaps your mum find out whether there are any local Al-anon meetings close by to you that you can attend. It will help you all deal with the challenges that come from living with an active alcoholic and will definitely help in some of your desision making around family events etc.
My daughter who is 21yrs has been to Al-anon but found some personal councelling/therapy more helpful when dealing with things to do with her alcoholic dad (my husband).
Keep reaching out.