Thanks for your response.   I think that I am going to back out of this,  D.   Why should I even go through a moment of angst for mother of a significant other of someone with whom I am casually friendly.   I've never met this man's significant other.   And I certainly know nothing about his mother.  

I will tell him that the tour leader of my group thought that I shouldn't do it.   That is the way I will finesse it.  

Thanks.   I just wasn't sure that I was overreacting or not.