I asked this because I’m a big baby.
I really like to get dressed up, but dh’s family is all very casual. My mil is usually dressed a bit nicer than everyone other than I in black pants and a sweater. Everyone else has on jeans. This one aunt almost always wears a sweatshirt with a collegiate logo on it. The men are in sweatshirts, t-shirts, or rather tired flannel shirts depending on the temperature.
What I really dislike is how incongruent all the photos wind up looking. I mean, I don’t expect everyone to be all coordinated as one might expect for professional family photos, but it always looks like a mish mash. Not a fan of looking bummy on Christmas 