Me and a friend (well, not really a friend) were once guests at a strangers house for Shabbos and my friend kept on downing glass after glass of wine. She ended up finishing an entire bottle and actually got drunk. It was not a pretty sight. (But she was the same girl who brought wine, beer and tequila on our high school shabbaton so her alcohol abuse issues started way before that) Needless to say, we were never invited back.
Moral of the story: …I guess the smart thing to do would be to not offer them alcohol but keep it on the table and if you see it getting out of hand, take it off the table.
And no, she is no longer my friend.