Ah, she's 20. I just responded on your other thread.
It's perfectly reasonable for you to ask her to meet him elsewhere. Alcoholics can be lovely people in their sober moments, and very charming and intelligent and witty. Unfortunately this is always a temporary state while in active alcoholism. They're not house trained! If your daughter has issues with this at 20 she can always get her own place and invite him round there, or she can go meet him at his place. Not your problem. Your house, your rules.
Note. They might not like this. BUT, they don't have to. They might think you're being mean, supporting their plans. Doesn't matter. You know you arent being mean but looking out for yourself. If the thought of disappointing them really worries you, it might be looking into that issue a bit more deeply. CoDa is a great fellowship, and their handbook can be very useful. And Codependent No More is a book that has really helped lots of people here.
BB