First of all, please know that everything I am about to say below is meant to be helpful and is offered in the spirit of "tough love" and tell-it-like-it-is good will...
Personally, Mahogany, I think you are making a mountain out of a molehill. Are they adults, in a relationship in which sex happens? Is it so wrong that an opportunity to have a little sexy fun presented itself, and they took it? I am sure they locked the door so no kids would walk in and find them.
. . . I realized that I was upset because: (1) He had asked me to sneak off with him and have some adult fun more than once during the party, and although I really wanted to, I said no. I didn't feel comfortable doing it upstairs when our kids and others were alert downstairs. So I put my responsibilities first (making an adult decision to wait). But he decided to go ask her, and SHE said yes. He continued to pursue it, even after I explained why it was not a good idea.
So, you didn't think it was a good idea, but she did. Why does that irk you so much? Is she supposed to be in total agreement with you about everything? Or is it that you are in charge of his sex life, and what you say goes?
Obviously, he thought it was a good idea. Again, what is the harm? Are they in an adult relationship or not? Are each of them in full charge of their bodies and sexuality, or do they need to run it by you every time they feel amorous? It sounds like you require them to seek your permission before they can fool around, and that smacks of a need to be in control of others. Keep in mind, that can only backfire, because feeling in control of what other people do is only an illusion. You simply can't control other people, no matter how many rules you pile on top of them.
In the past, I was fully aware of what was going the happen, so I had been able to mentally prepare, if you will. This was a complete surprise to me. Communication is very important to me, and they failed to do that. If they needed a date, they should have said that.
If they simply communicated to me that they NEEDED the time, they could have arranged a date for later that night.
I am curious why you need to mentally prepare yourself for when your husband has sex with his gf. Are you his keeper, his warden? You are aware he has another relationship, and that they are grown-ups who have sex. Why must they give you time to prepare? This seems like a very passive-aggressive way to try and put the brakes on their romantic/sexual relationship, because they can never be spontaneous in expressing their desire for each other for fear of upsetting you.
You wanted it cleared in advance and scheduled to your liking, so you could adjust mentally, emotionally, for some reason. Well, if I were either one of them, that would be a total buzzkill. Are you sure you have actually come to terms with what polyamory is, what it means to you and your partners, and how it translates in terms of real-world actions and choices?
There is a time and place for everything. If they would have taken some time to talk and connect, I would have been okay with that. Sex when kids are alert in the house is weird to me, and makes me feel uncomfortable. But I don't know if I am being too uptight about it.
I think your perspective is quite uptight, but it's probably something you inherited. If you read your words: "There is a time and place for everything..." that sounds like my grandmother talking. I'm picturing you wagging your finger at them while saying that. "Now, hubby, there is a time and place for everything, you bad boy!" I'm not saying that to be critical or mean, but to suggest that you take a look at your conditioning and how you let it totally throw you into a tailspin, and are using it now to justify being upset.
I am sure there are plenty of parents across the globe who have snuck away for a quickie while the kids were playing. And the world kept spinning.
I am at fault in not communicating clearly. I honestly didn't think that they would do that with the kids playing downstairs, and me downstairs too.
I don't engage in sex with him when she is unaware, if she is with us, because I feel it is disrespectful to her feelings.
How is having sex with your partner even remotely disrespectful to his other partner? If it is, then, is it really disrespectful of you if he has sex with her when you're available too? What is the logic behind that? I would think that she knows you two are adults who have sex, and it wouldn't hurt her to know you are doing it. Again, I think you are applying some sort of conditioned reasoning here which has nothing to do with the reality of the situation.
Sneaking off to enjoy each other, and leaving her out when she is around could be hurtful.
Why would it be hurtful? Can you see how you are using the situation to hurt yourself? In actuality, they didn't hurt you, but you are choosing to see it as a hurtful act.
Morally, I feel that it was wrong, because of when and how they went about it. Don't you think that it was the wrong time? We had 5 children downstairs with me. What if I wanted to enjoy the acts they were experiencing too, but I couldn't because I was downstairs taking care of the kids? Why do they get to go upstairs and enjoy each other? Why not me? ... To be honest, hubby had asked me to sneak off and do something with him earlier during the party, but I told him, "No, maybe later after everyone went to sleep." I guess he tried with her and hit the jackpot.
IT COULD HAVE BEEN YOU, BUT YOU REFUSED THE OFFER! You can't cry about not getting any after you turned him down! You want it both ways.
The above sentences I quoted really seem to speak to the crux of the matter, as I see it. You said no, and thought he should be satisfied with that. She said yes, and he got what he wanted from someone other than you. Honey, you are wrapped up in feeling jealous, possessive, competitive, and envious. You probably wish you'd said yes, but you didn't. So now you're telling yourself and the two of them that it's all about "time and place," and protecting the children, and being responsible. I call bullshit. You are kidding yourself, because you don't want to look at what's really underneath it. You want to be his first choice, you want to be enough for him, and you only want him to want her when you approve of the circumstances.
Believe me, I know it sucks to admit to feelings we don't want to have, but it's much more freeing and satisfying to be authentic than it is to hide behind some old life-limiting belief system.