Published elsewhere, in answer to a middle aged dad’s specific questions as to what is permissible for his demographic, particularly in dealing with teen aged children.
Sports jersey: You can wear it if it is a throwback jersey from the time you would have been the appropriate age — say an ugly 70s or 80s jersey. That would be cool — if anyone got it, anyway.
New music: The best way to do this is to find new songs you like but your kids hate. Play and sing them all the time. Or, if you can summon this out of your memory, annoy them by demonstrating how a new song is really just a copy of an older one you know and play the older one constantly. You’ll be right and they’ll know it but won’t want to admit it.
Hairstyle: The only change permitted is to something shorter — and shorter all around, not just on the sides or some other contemporary look.
Car window down: Absolutely, but no loud music. You can’t win no matter what you play. You don’t need the attention.
Talking to kids’ friends: Okay, but only about specific subjects, like sports teams they are on, colleges they are applying to, or anything admirable that they do that your kids refuse to do. “How’s your job going? Do you feel you’ve learned about [insert anything]?”
Social media: It will change faster than you can keep up, so pick a medium and stubbornly stick to it — with pride.
T-shirt: Your kids are right. Plain t-shirts are the best option in public at this point. It’s too much trouble to gauge your interlocutors’ appreciation for something else, and, if you think about it, you probably don’t really want them casting lengthy glances at your t-shirt to figure out what it says.
Collecting baseball cards and/or asking for autographs: Cards, sure, but why? You’ve got enough junk already and you won’t live long enough to find out if any of them are valuable. Autographs, no. I’ve tried a couple of times to approach a certain NBA player to get him to say one sentence I can film (it’s a joke for my daughter, and only makes sense from him) but it’s just too creepy to jockey for position with the earnest kids and youngsters.
“Dad’s” chair: Absolutely. There is no downside to this. Well, almost none. I once jokingly told my then ten year old daughter to get out of “my” chair. She jokingly told me, “take a hike, baldy.”
Food behavior: This is one of the unmitigated blessings of aging. You by all means should cling to your food habits and even take advantage to develop new ones that you’ve mostly been too polite to reveal. You just have to sigh and say, “I know I’m old and set in my ways, but I really don’t like…”
Good luck. There is no reason to go gently into the gloaming, but neither should you deck yourself in glow sticks.