From your boy's list, I love
Quentin,
Xavier,
Warren,
Garret,
Nicholas,
Samuel,
Kendall (I also like this for a girl),
Zaccai,
Rory, and
Thaddeus.
Malachy is an interesting spelling for
Malachi; I've only seen
Malakai and Malaky as alternatives. I actually quite enjoy it!
For the girls, I love
Dorothea,
Cressida,
Elspeth,
Rhiannon,
Saoirse,
Zephyrine,
Honoria, and
Avis.