AITA for inviting myself and my ex husband over to my in laws for Christmas, and not telling my ex wife.

I have a pretty boring/normal life but this is getting weird.<br><br>My ex wife (Liz) and I have 3 kids, M (20 m), E (18f) and C(17f). We divorced nearly 4 years ago. Neither of us has really dated, I'm kind of active on a dating app but nothing ever comes of it. Liz really doesn't want to date. We are both pretty busy with work and the kids. We're on pretty good terms, although not friends, we've been able to successfully co parent. We live a block away from each other and the kids go between the houses they want whenever. They've celebrated Christmas with me the last 3 years. <br><br>We weren't married a very long time before we divorced. We had only been together 5 or so years. We were able to come to a pretty amicable agreement. In exchange for a larger amount of money and a larger share of the house, I gave up alimony. That's why Liz doesn't need to work. I haven't gotten a Christmas with the kids because they say they feel bad, as obviously I make much more than Liz.<br><br>I get on pretty well with Liz's parents. Before we divorced they insisted on staying neutral, but obviously they're closer with their daughter. They have never said a bad word about me, but obviously not good either, they simply ignore me.<br><br>Liz's parents are chad and carol. They're wealthy and live in a big house outside of the city. They have an even bigger house at the ski resort we go to. The kids tend to spend a lot of their vacation time with their grandparents. And they've always spent Christmas at their house.<br><br>This year they decided to host Christmas (for the first time) at their ski house. They're having the whole family come, something like 70 people. Liz and I are the only ones with kids, and my kids are the only grandkids. They have a bunch of siblings, spouses and grandkids/nieces and nephews of their own. They put out an open invitation to Liz's siblings. They had planned to go without me, obviously. Liz and the kids were originally going, but my kids said they wanted to stay with me at home. I would have been fine with it either way, but Liz got pissed at them.<br><br>Here is where it get weird. Liz's father sent me a message out of the blue, asking me why I wasn't bringing the kids to Christmas, as obviously they were invited. I assumed he was Mistaking me for Liz, but when I realized he wasn't I played along. I told him the kids said they didn't want to go without me. He told me I was obviously invited as well. I asked what Liz thought and he said not to worry about that. <br><br>I wasn't going to do it initially, but once my kids found out, they insisted. They said it would be more fun than hiding out at home. And I have to admit, I was a little hurt by being shut out. I've spent the last 3 Christmases alone, with only a visit from the kids. Now it's not like my family is close by, but if it were the other way around I'd never exclude her.<br><br>Without telling Liz, I also invited my own parents. They were thrilled, as they have missed out on 5 years of holidays. Liz's parents were not. They said it wouldn't be a big deal, they'd just invite more of their family, but they were obviously annoyed.<br><br>This came to a head yesterday. Liz called me, extremely angry that I was bringing my parents to Christmas. She looked at the guest list, as the hotel sent out a list to be approved, and my folks were on it. I told her that her dad had invited me. She denied it, but when I showed her the texts she realized I wasn't lying. She has been pissed at me for the past 24 hours.<br><br>AITA?