That's hot, that you and your GF hooked up. I don't believe your BF would even consider that cheating given his lust for your past. I know if my wife came home tonight and said she made out, and other things, with another chick, I would be upset but also super hard and demanding pics and the full details.
Don't get me wrong, women can just as easily fill an emotional void left by a wife or GF's present mate. And I am guessing the number of relationship fatalities brought about by same gender affairs is growing. But IMO it isn't the same physically so it doesn't feel like as big a kick in the balls as another man penetrating my wife's pussy and mouth and spreading his seed(even if it is in a wrapper). Also men tend to think that you might actually share your GF's pussy if he displays understanding and forgiveness. Also mentally we can discount it easier cause we don't have tits and a pussy for our mates to get arroused by so we can kid ourselves that we did nothing wrong and that our wife or GF is just experimenting.
You are treading dangerous waters. Hyper Sexual women like my wife (and it seems like you too) have diffused boundaries when it comes to maintaining your mates expected exclusive rights to your sexual satisfaction. This is what our psychiatrist said to us during couples counseling and we totally believe it because her past has proved it. As in the case above, you have already madeout with another person, it just so happened it was a woman, but still a breach in that exclusivity. Albeit a really hot and boner-inducing breach that probably wouldn't get you in too much trouble but would put that "what else is she doing behind my back" doubt in his mind.
But now you are talking about going out with a woman that you have already breached the boundary with, and she will be introducing you to "friends" that most likely don't respect relationship boundaries and know how to play to your weaknesses, mainly cocks other then that of your current mate. Not a hard weakness to exploit.
I will be amazed if you go through with this get together and all you do is "hang out". It's like putting a drug buffet infront of recovering addict that has already expressed a desire to start doing drugs again AND has a partner that is somewhat fueling the growing desire. He isn't innocent in all this but he certainly isn't to blame.
Remember, your BF has already said "he is glad I'm not into it now" in a previous post. It would have been a lot easier on both of you if he would have either said "I don't want to hear about it and if it happens with us, we're through" OR "do you think we could invite someone over for you to fuck infront of me, I have always wanted my GF to be like you". But he didn't, he, like alot of men, got excited and disgusted at the same time. His inability or unwillingness to demand exclusivity "OR ELSE" has left the door open. He probably isn't even aware of that fact though and thinks he has a loving and faithful GF that wouldn't dare cheat cause she would lose the most wonderful man she has ever met, aka him.
It's the arrogance some of us men have about our unfaltering ability to keep a mate, regardless of how we treat them or take them for granted, that is eventually our downfall.
Just be aware that you may be like my wife and that your boundaries that were inplace at the start of your current relationship, are quickly eroding and by surrounding yourself with friends of a like mind with no respect for your current relationship will be the end of it. So either reign yourself in, ask your BF to communicate honestly what his reaction would be to you fucking another man or roll the dice and deal with it later.
You have to think about it seriously, because you have described him as your "sweet mr. perfect" boyfriend. I think your mr. perfect would have to already be into sharing honestly. If you aren't willing or just can't give him some time to catch up to your liberated outlook on sex, then mr. perfect may do a 180 and become mr. nightmare. OR like me, he may forgive your indiscretions because he really does love you for you and has truly fallen for you. OR he could be a true cuck at heart and needs a dominant, don't give me any shit, super-***** to put him in his place.
Very confusing I know, but such is life. If we all subscribed to one ideology and it's teachings there would be no conflict and everything would be vanilla and lovely. But being human, it's what we're good at, conflict and resolution I mean, and we have been that way since the beginning of time.
You obviously have the conflict part down no problem. But now YOU need to provide the resolution because as much as this board and others might be able to give you insight, share experiences and open new paths to a resolution, only you can tailor all of that to the outcome you desire.
I know, I can be very deep when I want. We aren't knuckle-dragging, dick-swinging apes ALL the time.