If I let my wife have sex with another man while I watch is that wrong in any way?

Why on earth would you want to watch another man do your wife ? I think you should spend the time and energy doing your own wife. This is only my opinion non judgemental.

If she is happy to do it I dont see any probelm

I have done this recently and am struggling with it. On one hand, I am not the most compatible with her in bed. I have had other lovers that had better chemistry and she has had the same. So we gradually have had less sex since it was not as enjoyable. We decided to try introducing a younger, healthier, and better endowed man to trigger a much needed interest. Boy, did he deliver, now she wants it again. We have rules in place so there is no confusion, and she is loyal to me. But it is a strange pain I feel that we have opened the doors to something dangerous.