Still an invitation?

Dear Annie: I have a family problem for which I would appreciate your opinion. My wife and I are Americans living in a small village in Italy, in an area popular with tourists. Recently, I contacted my sister and her husband from the States and expressed our interest in having them visit us and stay at our house, since we haven’t seen them for many years. We’re all retired, they easily have the means to make the trip, and our house has plenty of room for visitors.
Her reply caught me unprepared. She said that they were expected by their church to do a mission outside the U.S. and, based on my invitation, they were requesting Italy as an assignment.
I am areligious, as is my wife. My sister and husband belong to one of those American evangelical religions that cropped up in the U.S. in the 19th century. By contrast, the culture of our village and the surrounding towns is, of course, primarily Catholic, even though most of our neighbors seem to be secular.

My problem is this: We are known in the area as the only Americans living here. Were my sister and her husband to go door to door, or set up a display at a local piazza, our neighbors would know we’re the source of the strangers hassling them with unwelcome proselytizing. I can assure you they wouldn’t appreciate it, and neither would we.

I’m at a loss of what to do. My sister and I aren’t on terrific terms, due both to our differences in lifestyle as well as typical family friction from long ago. I’m certain she would be offended if I were to suggest she not proselytize during her visit, but I’m equally certain our neighbors would be offended by her doing so, and the repercussions of that would last long after she and her husband returned to her hometown.

I can see three options: 1) ask her to not proselytize on her visit; 2) do nothing, let things run their course and deal with the repercussions; or 3) withdraw the invitation.

None of those three options is particularly appealing. I’m writing to you to see if you could suggest a fourth. -- A Fourth Answer

Dear Fourth: Tell your sister that you invited her and her husband for a family visit and not a church mission. You should let her know of your concern with being the only American couple living where you do and that her proselytizing might be offensive to your Catholic neighbors and would tarnish your reputation. Let her know that you really want to see her but only as a family visit. If she declines, so be it.

So if your sister informed you that you would only be welcome as a family visit -
what would be your answer?