OK, you've had your vent. Now you get to use your brains.
I'm outside the situation, so I don't have to feel all the drama. I can just look at the fact that you have a lot of relatives nearby.
If I were the one in this, I would sit down with my husband and discuss it, because we'd have to have a solid, united plan. We would look at the number of relatives who expect us, and the rest of the activities the season brings. I would stop thinking Christmas Day and think Christmas SEASON - from early December through New Year's.
Then it would be time for US - meaning YOU - to take the initiative. Your husband can tell his mother that, say, you are able to come Thanksgiving from this time to that time (if you come at all). If that excludes Thanksgiving dinner, he can say, "We don't mind, because it's seeing you that's most important to us." Fix a few days during that season to devote to your aunt. You could have an early Christmas, or a late Christmas, with FIL. You could enjoy New Year's with MIL, or somebody else on the list. You could work out times to be with your parents and the rest of your family. You can't see everybody when everybody wants you to come. But you can see everybody, or mostly everybody, and your children can enjoy their kinfolks that way.
Christmas itself... you have other plans. You're starting your own traditions for Christmas day. That's your story, and you're sticking to it (as the song goes). Just make sure you don't leave anyone out of your planning for the rest of the time.
Now, you can't do this and NOT be called a jerk. So you have to decide whether you and your husband own your Christmas season, or if everyone else owns you. You may well find that, after the initial loud sputtering, the others will all settle down and say, "Well, that's the way they do it, so I guess we'll have to put up with it." And they will adjust, when they realize how glad you are to see them and how comfortable they feel with you - no arguments, no backbiting, no extra drama. If one or another of the relatives prefers to write you off, just go along with that ("We wish you the best"), keep being gracious to that person, stick to your guns, and next year might be different. (Next year, you'll be able to say, "Last year was wonderful! We had the best Christmas Day - our children loved it and so did their parents. We're happy to make that a permanent tradition now.")
You're getting needled because you're being wishy-washy, saying, "Well, I don't know... I'll get back to you." Make the decisions and stick with 'em.
I'm a MIL myself. Yes, a hated MIL! We volunteer to have everybody for Christmas at our house. If the children and grandchildren can come, they're more than welcome! Sometimes they can't. Sometimes they just don't want to! I do request an RSVP, so we'll know whom to expect (and not expect). A few years ago, one of the married children wanted everyone to come for Christmas at their house instead. So we all planned for that - and then, at the last minute, they changed their minds. It was a real scramble, and sometimes folks don't realize what hosting a dinner any time of year entails. Please decide, and then leave the answering machine on if you need it to handle the complaints, but enough with the "I'll let you know" business! "Woman up" and make your decisions! It may feel like walking the plank, but once you and your husband stand up for your family, you'll feel better about the whole thing.