So I'm going to split this into categories: Kids, Jobs (maybe as a part time thing alongside being a Ninja)  and Residences.

Onto the headcanons!

Jay/Nya:

Residence: Cliff's mansion

Kids: I like to think they'd have two kids; a younger boy named Gordon and his older sister, Abby (yes, the name and character was indeed inspired by MasterofCupcakes 's Long Time No See). I like to think that Gordon is the shyer one, having water powers, fair skin, dark brown hair and brown-ish eyes. Abby, on the other hand, has water powers, blue eyes, dark skin and black hair. She's also a lot more confident and social.

Jobs: I imagine them being part-time mechanics and helping out the city with their inventions.

Lloyd:

Residence: Probably the Monastery

Kids: Let him find a partner first. But I do think he'd have two sons like his grandfather (or maybe two daughters this time?)

Jobs: Just protecting the city and teaching the new Ninja.

Wu:

Residence: The Monastery

Kids: Uh, too old.

Jobs: Being a Sensei and a teacher to the team's kids besides Lloyd.

Cole:

Residence: Somewhere in Ninjago City near his dad since they fixed their relationship.

Kids: If he had a partner, I think he'd have two twin boys. He just seems like a twin person.

Jobs: Trying to cook. Emphasize on trying.

Zane/Pixal:

Residence: Somewhere close to Borg's in Ninjago City.

Kids: I think they would build a little robot daughter/son.

Jobs: Helping Borg out in his company.

Kai/Skylor:

Residence: Some place near the noodle shop, even if Kai wanted to be a little closer to Ignacia.

Kids: I imagine them having a daughter named Amber. Just imagine a redhead with Kai's spiky hair!

Jobs: Probably just the noodle shop.