So I've had a mfm threesome once with an ex and a best friend. None of us had any performance issues. My opinion is that a lot of this is mental. If sex is mechanically setup and scheduled.... Then you're not going to get into it or maybe as in this case, the other party isn't.
Have a date with your wife wearing some hot stuff... Don't make it sound like a sure deal. That's bound to get some lust flowing on both sides. With me, we were talking flirtatiously about the idea for a long while and then we just sorta all dared each other and no one was backing down and it happened. My friend continued to steal chances to feel up my ex when I wasn't around etc which was hot when she told me after but full on sex never happened again
Have a date with your wife wearing some hot stuff... Don't make it sound like a sure deal. That's bound to get some lust flowing on both sides. With me, we were talking flirtatiously about the idea for a long while and then we just sorta all dared each other and no one was backing down and it happened. My friend continued to steal chances to feel up my ex when I wasn't around etc which was hot when she told me after but full on sex never happened again