You said your both open to things.
Your simply an exhibionist. Should be easy to discuss your likes & he may be fine with it too. (Start slow/mild & be ready to be patient). Just don't cheat or you will get what you most fear.
I was into this with an ex, and while it's not impossible to do and make it work as a couple, the risk to your relationship is high. Communication, a list of dos and don't, and all people involved have an equal say on what goes and what doesn't is a first step. Boundaries have to be set, respected, and followed 100%, even in the heat of the moment. Expect arguments and jealousy to rear it's head afterwards, but talk it through thoroughly before, and especially afterwards. If you think you want another guy to join, do it before getting with another girl first, otherwise you probably won't get to do it afterwards, regardless of how much he promises before hand. Write everything out on paper on what is agreed upon, and sign it, so there's no question about what was said later. Don't get with friends, only people you don't know, and only women talk to women, men talk to men to keep everyone above board. Also allow each other to look at phones, laptops, emails at any time without question. These are what I learned in over 2 years of swinging, and it still came back to bite me
I will say ask yourself if it's worth losing your life that you've built for yourselves. I had a lot, and I mean a LOT of fun, but would I do it again? Hell no, as the pain and betrayal of my ex leaving me for a friend and lying to me destroyed me for many years.
It sounds like you need another couple. Him to watch and her to participate. There are lots of couples like those in swinging circles.