Mari would probably be an editor for a company (making artwork, logos, ads etc) mostly because she isn't good at anything else and retail would be hell for her ;-; (she wouldn't likely hold a high position either, because that means speeches and she HATES that) She might also do youtube in her freetime, being anonymous and making vids of her favorite fandoms n stuff
Kel would be a solo pianist, making background music for those aesthetic games n such (which would probably go viral at least twice)
Idk abt Elias because his frail body would disallow him from most jobs (if he ever got a cure though he'd probably be a doctor/scientist and research his way to cure other diseases n such)