The dominant type of VN is Japanese 18+ eroge, so if they can deal with cartoon porn, they pretty much could accept the genre as a whole. I would probably suggest something that has some mild sexual content or fan-services with a simple decent story suitable for light reading, but has a significant impact on its conclusion and can generate a feeling that it would be pretty awesome if it were to be turned into an anime.
Yea, something like G-Senjou no Maou.
I could give them Clannad, Rewrite, or Ever17, or even gameplay handheld VN such as 999 and Danganronpa, but that would not break a false stereotype. It would only be like erm.. "acceptable" titles surrounded by a pile of cartoon porn shit. They probably will open up to all-ages, but I think they will still shun 18+ titles. If I have only one shot at this, the best thing is to pick a 18+ title. Anyone who can't accept it by then simply isn't cut out for this medium.