How can I have this thread deleted…just in case?
Too late. We’ll see you at 7pm.
I will counter with a differing opinion. I think you will be setting a precedent by starting a new Christmas Eve tradition and including this couple. So you are not deciding on one night, but on expectations for many holidays yet to come.
I think on Christmas Eve you get to focus on what your immediate family wants. How THEY want to spend that evening.
Just knowing you will spend the evening with this guy will dampen the joy. Every moment he will be occupying space in your head as you imagine what awful thing he will say next. It is not worth it. You will not win a fight with him. He will dampen the whole evening.
Since you have had other gatherings that did not include this couple, you have precedent to have a small gathering that doesn’t include them.
Later on, when this comes up in conversation, you can keep the talk light and mention your H was concerned about the evening turning into a huge party instead of the intimate and relaxed dinner he was looking forward to.
Then invite your friend to something special for just the two of you.
In a situation like this I usually suggest putting yourself in their shoes - or the wife’s at least. How would you feel?
Be prepared to steer any conversation that seems unfavorable. You can do it! 
I’m with @powercropper in general on this one. Why invite anyone to an event that you don’t enjoy spending time with? Of course family events like weddings are different, but I wouldn’t invite them to
this. So what if they find out? You are adults, not middle schoolers. People are allowed to have varied social groups. No one is owed an invitation to anyone else’s party.
So this is why we never get invited anywhere! 
Isn’t is weird how holidays shine a spotlight on odd relationships and cause much consideration of the ‘right thing’ to do versus what you want to do!
We have a family member who we never see, who had a verbal kerfuffle with one of us many years ago and things have been weird ever since. I have made the obligatory (because ‘everyone’ knows I do a nice dinner?) invite for many years for Christmas Day. She always brings in a weird vibe & we all know she has never preferred my DH, but the last 5-10 years she often does not even say hello or good-bye to him, to the room, yes, to him, nothing. He feels it, the kids feel it, everyone agrees that it is just plain rude and weird.
This year has been hectic and intense due to other family obligations plus we have a new baby and a new spouse in the immediate family picture, we have decided we just want to be us, not ruin that special and rare family time together with her weird off putting, everyone feels awkward vibe. I just don’t have it in me to be the social guardian this year, including all, watchful to turn conversations to better directions, etc.
And I still feel like a bad person for not inviting her, because, well, family is supposed to be inclusive.
@somemom Yes, families are supposed to be inclusive, but that family member has pointedly not included your H, her host, for years. IMO there is absolutely no need to feel like a bad person for not continuing to invite a person who has not extended even basic courtesy to your H (like saying hi) over the last five plus years. Hold those who are close to you dear and enjoy their company this holiday season.
I have a long time not-close friend who’s husband almost everyone can’t stand. I never go to anything she invites me to at her house because he is such a pain. Some other friends go/others don’t. But I do feel for her and we enjoy our company when we are alone/with friends without him.
I typically veer towards being inclusive but maybe this sentence of yours can give you an out: " I know she typically does something small with another family we don’t know, but don’t know if she is this year." One could assume not to invite her as you know she usually has this standing engagement?
One suggestion: if they come, and if the husband is annoying as usual, be prepared for your own husband’s “I told you so.”
@conmama What a generous act to invite them, especially on Christmas Eve.
When I have to interact with someone I don’t care for, my trick is to remember that I only have to deal with them for a brief time. It costs me very little to be pleasant for a few hours, whereas this man’s wife and son have to deal with him every day.
Adding to the good idea about “That’s nice,” from @bearcatfan : H is a really patient listener. When my dad or my FIL drones on about, well, lots of things, he just keeps making eye contact and asks, “Is that right?” periodically. They’re happy to have someone to talk to, and H doesn’t get frustrated because he’s only half paying attention (he usually has one ear on a ball game, but he hides it well).
You could make it a game for your family. Like family bingo night with projected boorish remarks on the cards.
“Is that really your hair or did you get a new hat?”
“Someone with your butt shouldn’t wear horizontal stripes.”
“This turkey/ ham/ roast beef is dry”
“No one like (your child’s) college”
“You’ll never get a job in that major”
“Oh that’s a handbag? I thought it was an ashtray”
@somemom that’s a difficult situation. I really am not sure I could host someone in our home that refused to greet my H or any other immediate family member for that matter. It’s one thing putting up with a difficult personality for a few hours – I am certainly capable of that and do it all the time. But not sure I would excuse or even invite someone who would not abide by the very basic social norm of greeting your hosts and at the end of the evening thanking them.
Guess it would depend on how my spouse felt about it but I don’t like the message that sends.
lol, we were that couple for quite a few years. My H went through 10 yrs or so of being a incorrigible ‘mansplainer’ and is conservative while all our close friends are quite liberal. Thankfully, my H mellowed with age. I was saved 5 years ago when my best friend re-married a mansplainer herself and the two men now go in the corner and talk to each other. I was a bit worried with the election that we would be shunned for 4 years if my H voted for Trump—he goes back and forth between parties. My best friend looked up if anyone in our precinct voted for Trump. Thankfully noone did, which means H will not be socially blacklisted (I didn’t know since we practice don’t ask/don’t tell re politics).
Along those same lines, whenever we encounter a person like that, DH says, “Just think, that poor guy has to live with himself 24/7!” For some reason, that really helps my attitude. 
“My best friend looked up if anyone in our precinct voted for Trump.” Where’s your neighborhood and are there houses for sale? I’m ready to move there. 
https://www.youtube.com/watch?v=vKOb-kmOgpI
Sometimes no good deed goes unpunished. I used to invite a longtime friend to parties, holiday meals, etc. Few people liked her, she was very negative and a chronic complainer and she had no insight into her behavior (eg “I sat at a table and no one joined me. What is the matter with them?”) . I finally distanced myself. Its sad to essentially have no more contact, but when I realized there was little enjoyment from it, I decided there was little point to doing what I felt only obligated to do.
I can understanding wanting to invite the family, if you like the wife and son. It is hard, because if your H finds the other husband to be overbearing and unpleasant, it can ruin the evening for him, it doesn’t take much for one person to poison the waters. I wonder how many people invite them to things if the H is that way, and I wonder if the wife realizes how people feel about him…
Hopefully they will otherwise be engaged if you make the invite to them. On the other hand, if the other couples and your H have any sense, they will understand why you invited them and respect your wishes and understand how awkward it is for you. I faced something like this with a couple where the wife had a religious epiphany of some sort and at gatherings would decide, especially on something like Christmas parties, to ‘share the good word’ and not in a good way (she was frankly obnoxious). I actually talked to the husband about it after the last party, he hadn’t realized she was doing the stuff she was, and at first the wife refused to come to gatherings after H talked to her (H came with the kids, and they were all nice people), and then eventually realized she had been making others uncomfortable and toned down, and the last time I saw them it wasn’t an issue.
Now, see, the guy I was talking about does things like talking about motorboating ladies boobs.