@redbird1979 – well well well. Wow. Has to be exciting. I unfortunately have about as much experience here as I do flying fighter jets, so I may not be the best person to ask when it comes to multiple partners.
I am hoping some people in the comments will chime in.
I kind of have a personal rule on multiple partners, but first, remember that all people are different and what works for you and him is something different than what works for me.
In a relationship, I’d never go there if you think jealousy will be a factor in your head, even if you slightly think it might, because it will surface during or right after, from what I have heard from other. If you think he will be okay with another guy inside you, and you will be okay with him inside a girl – then I think that is awesome and have fun and make some amazing memories. My suggestions? I’d make sure everyone is responsible, tested, proves it, and understands each others safewords.
For me, I am just not built that way. I am not a jealous guy, to the point that it has bothered people I am not more so. I guess I just trust people and think “go ahead – he ain’t me”. However, I may not be jealous, but I am very territorial, and I just would not allow another guy in my girl and wouldn’t want to ask that of a girl I was with. The only way I think I’d do it would be a true lesbian, who had no contact with me, and I was with my girl and she was too, but even then I’d have reservations. I think it is those “reservations” you may want to be mindful of, if they exist.
But if you know for certain that your relationship will be strong after, I say “lucky fucking you”. Have a blast. I am sure it will be hot as hell.