Aphrodite kids are always the first to know someone's sexuality
Like they took one look at Nico di Angelo and went "gay" but they have sworn each other to secrecy not to share
They are the ultimate wing people, even if they don't know a person they will ship them with another person and try to give the two of them opportunities to be alone together
And usually, they're right

The party ponies LOVE football.
To the point that on super bowl Sunday, they hold a massive convention in the city where the super bowl is being held, drink root beer, bet on the winning team, and anyone who loses the bet gets paintballed. They also play football themselves, except it gets very violent and many centaurs end up as a pile of dust. But they're motivated enough to get back up from Tartarus in the same day to keep going
During the halftime show, they sing along if they know the songs but they're all drunk on root beer and end up just stumbling around screaming random lyrics and trampling each other
Dionysus often attends these parties, because although he isn't allowed to get drunk himself he still finds it entertaining to watch the party ponies get drunk

Every holiday season the Aphrodite kids that stayed over winter conspire with the Demeter cabin to grow mistletoe. Everywhere. Sometimes spontaneously over people who they think it would be funny.
Half of the campers think it's hilarious. The other half get caught under mistletoe with their platonic friends/crushes/rivals and get peer pressured.

On Valentine's day, the nicer Aphrodite kids who happen to stay over the winter buy boxes of chocolates and hand them out to everyone
Because "platonic love is love too"

A
A

A

nd the other campers think it's cringe but they get chocolates and it makes some of the more introverted ones feel like they're worth something so no one complains

The Apollo kids rehearse and perform skits in the amphitheater, and at the end of each summer they put on a big play with the Hephaestus cabin helping with set design.
It's something the whole camp looks forward to, right up there with the chariot races and the fireworks.

I'll post more headcanons soon, these are all the ones I came up with over my break