When one of my brothers visits, he smokes outside. When we visit the other brother who also smokes, he just stands downwind.
The third brother doesn't smoke, hurrah!
The greater issue for us was teaching our children to be polite about it. I think because the WoW is such a black-and-white rule, and one that's easy for kids to grasp, children tend to get carried away with zeal about it. I guess that goes for some adults, too. I talked to my kids about addictions, agency, and family love. In spite of seeing their much-beloved uncles smoke, neither of them has taken up tobacco.
That said, no notable alteration of behavior/personality comes from smoking, while someone using alcohol may be offputting to a reserved child. In your shoes, I'd lovingly ask my family to be very sparing when in my home. Only if they distress my kids would I demand a ban.
I do wonder, though, if your family members are just "social drinkers," why would there be such a need as to drink in the car before coming in to eat? They're either addicted or terribly immature.