To Threesome Or Not To Threesome

I declined those times because I just wasn't quite sure if performance would have been an issue with another dude in the room. I'm not homophobic or anything like that, but it's just I don't know that I could keep things up if ya know what I mean. So fast forward to now and this is a different deal, two chicks and me. But if I accept, does this open Pandora's box and am I then obligated to throw a threesome at my wife with another dude? Cause if that's the case, I don't know if I'm down for that.