Someone Who Can Do Alcoholic Math?

I need help. If, say, one was giving a bridal shower/cocktail party....how much wine and beer should one buy? There are going to be appetizers for nibbling. There are going to be around 15 or so adults of drinking age, though I'm not sure how many of them do drink, will drink, or how much they might drink. The soiree is from 5-7, so happy hour-ish. At least ten of the people will be driving from about an hour away, so this would probably prevent at least 4 of those people from drinking a whole lot. So this is my math problem to you:

If 5 cars containing 11 people traveling 60 miles per hour arrived at my house where there are already 4 other adults at 5:00pm on a Saturday and remained until 7:00pm, how many bottles of wine and how many beers should I purchase? Show your work.