I imagine there are a lot of wives who hesitate about Swinging or threesomes because they feel they have some flaw that makes them unattractive to other males. My wife was such a woman. She has a good sized scar on her left right butt cheek. Of course it's covered all of the time except during sex. (she won't even wear a bikini) When I mentioned we should try Swinging, she wouldn't hear of it. It took months of convincing her to agree to a MFM threesome with a male family friend.
I think it did wonders for her self esteem. The friend didn't mention the scar at all, my wife was extra amorous with him and I assured her she was desirable. I kissed her passionately as she rode another mans dick. I whispered to her, "Let me know when you feel him cum inside you". That really turned her on. Knowing that men were horny for her body.