I would choose
Bryony, I like that spelling better as well because the placement of the "rio" looks a bit strange in
Briony.
I don't really like
Alcyone, probably because I used it as a last name for my Sims, haha. Plus, if read too quickly many will pronounce it as "al-sai-on" (with a soft-S sound rather than more of a soft-C sound)