Melanie is darling. It sounds great on a child and an adult. Nice job.
From your list I like
Melanie Claire, and
Melanie Kate.
The meanings are redundant, but I've always liked the sound of
Melanie Kiera /
Ciara ("KEER-uh"). I suppose if you use
Kira you'd get the same sound but a different meaning. I just don't like the look of
Melanie Kira as much.
Melanie Carys sounds nice too. I'm getting a real K sound vibe with
Melanie.