Wife and college friend

I have a dilemna. I still get together with an old college friend of mine. He was quite the Don Juan in college. He and I got married around the the same time and we socialize as couples too. Unfortunately his wife had some female health issues which ultimately has led to a complete vaginal reconstruction. Even with that intercourse is painful so much she has told my friend no more sex. My friend, Jerry, has complained to me about it on numerous ocassions. So much so, after several drinks one night, I had jokingly told him I would loan him my wife. He readily agreed and I tried to tell him it was only a joke but afterwards he told his wife who talked to my wife and apparently all agreed. When my wife approached me about it she accepted that I was not serious at the time but under the circumstances thought it would be ok. I told her I didn't think she was capable of having sex without forming some emotional bond. She disagreed and said that this would be strictly sex. At this point, to try to dissuade her, I tried to up the ante by saying if I agreed I would want to photograph and video the episodes. This is something she would never allow in the past. She thought about it for a minute or so and then said ok as long as it is kept private and not put on the internet. This tells me she very interested in doing this but I'm afraid it could change or damage our relationship forever. Thoughts, comments?