Congratulations! As your boys names are all 4 letters it seems in theme to keep baby girl’s 4 too.
of your list I like:
Cece - love this as a nn but not so sure as a full name (could be a nn for any C names though!) so what about Cali, Cora, Cara? Or slightly longer - Clara
Etta - I think this is the best one of your list! Gorgeous.
Iris - lovely but quite a mouthful with Otis
Leo - love this but people may assume you to have 4 DS when they just hear names- if that doesn’t bother you I do think it’s quite cool for a little girl
Other suggestions:
Rafe, Milo, Otis & Ayla
Rafe, Milo, Otis & Alys
Rafe, Milo, Otis & Anna
Rafe, Milo, Otis & Emma
Rafe, Milo, Otis & Alma
Rafe, Milo, Otis & Nora
Rafe, Milo, Otis & Leah
Rafe, Milo, Otis & Inés
Rafe, Milo, Otis & Wren