I don't see if you put food on, you necessarily have to serve alcohol at a lunch. In fact, I would think most people would bring their own booze if you were catering. Maybe it's culturally different here, but I think most here would take their own booze along to a lunch.
Dinner party is a bit different and I have some wine at hand, but again, I still think people should bring a bottle of wine as a gesture, so really I wouldn't be over catering on the wine.