The vendor's negligence was not in selling the product to the father, but in his failure to plainly identify it as an alcoholic beverage on his menu placard. If his menu had listed available non-alcoholic beverages and alcoholic beverages separately, the mistake would never have happened.

I don't drink. That means that when I'm making a beverage choice for myself I ignore beer and wine lists. Simple enough. It's apparent that the father in this case wasn't afforded that simple tool to help him make his decision.