Wife sharing, iin?

I've been married to my second wife for 16 years. There is 16 year age difference between us. My first wife cheated on me.When I met my present wife I began to fantasize about her with another man. I finally told her about it and she wasn't shocked or appalled, she said it was very brave of me to share that with her. We talked about it more and she admitted that she had always fantasized about having two men at the same time. I wanted to make this happen. I posted a personals ad and we got 40 replies. She found the weeding out and qualify process to be a pain. She didn't really want to chat with them she just wanted to fuck them. We met one guy at a bar, talked for a while and went to a sauna. It was very sexy at first as we undressed and got into the water. I became very excited when he started touching her, and she moved over and straddled him. He pulled himself out of the water and sat on the edge of the tub. My wife got between his legs and licked and sucked him. I was so revved up I could hardly breath. We moved over to a small bed, and she mounted him. He however had trouble staying hard and couldn't penetrate her. He finished in her mouth. It was a great experience for me but my wife was less than satisfied. We had a few more unsatisfactory encounters and some very good ones. We also had some good and not so good times at swing clubs. I always made all the arrangements and talk her into going. She grew tired of this and said she didn't do it any more, she just wanted to be with me. I tried very hard to put my fantasies away and go back to being a normal couple. It wasn't easy. As years went by we went through other life events. She care for me as I went through a life threatening illness. We grew closer than ever. Our sex life faded. Recently she came to me and said that there was a man who had flirted with her and she had flirted with him. She wanted me to tell her if I would mind if she let things follow there course, if she could have sex with him, It would not be like before, where I would be there to watch, she would go of to see him and then come back home and tell me about it. This made me very uneasy and excited at the same time. I felt it would be hypocritical for me to say no after all we we've been through. Still not being there is very new and different.