YABU I’m afraid. If DIL insisted your DS attend with her every year I would say, it would be okay to ask DS if he’d mind coming on his own to your family celebrations (with a caveat that if he doesn’t want to that’s fine too), but that’s not the case. He can go yours if he wants to and he sometimes does!
I hate Christmas precisely because of all this pressure. My family are quiet introverts, but Christmas is a big deal, it’s Christian, we go to midnight mass, my mother is an incredible cook, so the food is amazing, she is amazing at decorating so the house looks like a Folksy German concoction and presents aren’t really a thing, we make something handmade to gift each other, it’s more about being together, without any monetary gifting stress.
However I can’t attend family Christmas’s as my family live on the other side of the world. Because of this MIL expects us to attend every family Christmas with her.
I can’t bear her Christmas’s. The emphasis is on spending money on gifts as a couple saving for a house we can’t afford (they are well off), they are loud and binge drink, the food is beyond awful, we both hate it and there is no room in the day for us to do any of the things we’d enjoy, say a country walk or a nap when the volume gets too much.
The one Christmas we had alone she threw a massive strop, but oh wow it was the best Christmas we’ve both ever had together. This year we have a baby on the way, and we will use this to break the chain. It will be Christmas’s just our nuclear family from now on, and we can celebrate with them on another day, like Boxing Day.
My mil had her wedding planned by her mil, her Christmass taken over by her mil, her childcare taken over by her mil so she now tells me it’s my turn to make that sacrifice too. But actually it’s not. It was her choice to let her mil dictate her life, as it was yours to equally divy up Christmas’s. Just because you did that it doesn’t follow it’s fair for dil to do it too.
Your dil has siblings that live overseas, moments where everyone is able to come together (especially before children arrive to put a spanner in the works) I’m guessing are rare. This isn’t about Christmas so much is it is about DIL getting to see everyone all together at once. Don’t poison it by stating your displeasure with your son. You are lucky you have a great relationship with DIL, that too is rare, so safeguard it by not letting her or your ds know your disappointment and if you want him there, just ask if he would come this year.