Mother’s Day expectations

For starters, my parents are moving. For a variety of reasons (kids, available babysitters, etc.), we only have one weekend my husband and I are able to assist them with packing, moving things. That weekend happens to be Mother’s Day weekend. My kids have soccer Saturday morning, and my husband and I were going to attend their games, and then drive to my parents to help them with moving (they live 3 hours away). So, we’d be there Saturday evening probably around 5, and were going to come back Sunday afternoon. My MIL agreed to watch the kids, said “of course, you need to help them.” She was a little snarky at first when she agreed, saying “it’s my day, but I guess I can watch the kids for part of the day.” insert eye roll I mean, it’s not exactly what I want to be spending my Mother’s Day doing either, packing and driving, but I’m trying to help my parents, and it will be nice to be with my mom either way.

MIL just called husband and said we need to be back by noon on Sunday (mind you it’s a 3 hour drive), because she needs to go to DH’s grandmas house, for a Mother’s Day gathering. She told us we’re invited, but we have to be back by noon. First off, that barely gives us time to help my parents, after she agreed we needed to help them, and agreed to watch the kids. Second, that’s not how I want to spend my Mother’s Day, going to his family’s gathering. So, I’m supposed to tell my mom to buzz off Sunday morning, because I have to be home for what MIL wants to do? After this phone call, husband basically shrugged his shoulders at me, said “well that’s what she wants, and she’s agreeing to watch the kids.” So forget what I want? I’m of the opinion that his mom/grandma had their years of celebrating Mother’s Day when they were in the trenches with kids. I have 3 kids, am currently in the trenches, and deserve to be celebrated. I don’t want to share my day with his family, and I am insulted that she thinks that husband should just drag me along to something that she clearly sees as a celebration for her, because she’s “mom.”

Am I in the wrong for thinking she’s being selfish? She agreed to help, but she’s backing out on half the commitment. And she’s ignoring the fact that it’s not just “her day” but my day, and my mom’s day as well.
My husband always caves to what she wants, and we’ve had many discussions about how I feel he puts more effort into trying to make her happy than me, especially when it comes to holidays. He agrees his mother is annoying, overbearing, etc, but he never calls her out on her bs. I’m at a loss for what to do though, because she’s helping with watching the kids.