Xenia: I don't think pronunciation would be a problem. In fact, Zena/Xena/Zina is not pronounced the same way as
Xenia so that's not spelling it phonetically.
Not crazy about
Xenia though. It sounds like part of a medical term.
Caoimhe: This definitely seems pretentious and show-off on a child of non Irish parents. Even on an Irish child it seems over the top. The spelling makes no sense to anybody not very familiar with Irish language. The pronunciation
Keeva is not very attractive anyway, it sounds like a sport utility vehicle.