There could be a story where the wife is an artist. The son's friend shows an interest in art. So, she starts to teach him some basic drawing techniques. They end up having a great time together, with the wife inspiring the young boy to see the beauty in the world around him and express it through art.
Perhaps the wife is a great cook and when the son's friend visits, she always bakes delicious cookies. The son's friend starts to see her as a second mother figure. He might share his dreams and problems with her while enjoying the treats, and she gives him good advice on how to deal with things like peer pressure or choosing a hobby.