How about Oliver, Roman &
Sebastian
Emrys
Tobias
Atticus
Silas
Hugo
Archer (nn Archie)
Charles (nn Charlie, Arlo or Archie)
Malachi
Wesley/ Westley
Jasper
Kasper / Casper
Ambrose
Cyrus (nn Cy)
Matteo
Felix
I find Levi too close to Oliver (letters wise) and Phoenix too out of genre (often families give the wild name to the youngest/younger having given the most classic to the eldest/future leaders, lol). August and Cillian work imo. August is nice so all get their own starting letter and ending sounds, but Cillian is more interesting these days.
As for your girls, I really like Zara. She has such international charm and sparkle with your other two! Athena is a little on the nose with Roman.
Otherwise:
Lydia
Celeste
Zoe
Iris
Elodie
Sofia
Claudia
Leonor
Helena
Tabitha
Daphne
Aurelia
Elara
Imogen
Martha
Delphine