Lucy Bronwen Sinead is wonderful. Not sure how you can think that
BronwYn is a Welsh girl name ... perhaps a typo?
Holly and
Molly are very fashionable and could well date her.
Heidi Darcy doesn't sound good, even with another name in between. I suppose if it was me I'd consider
Ada, though it's also very contemporary, unlike the timeless
Lucy. What about
Polly or
Mildred nn
Milly instead of
Molly;
Helen instead of
Holly;
Sigrid instead of
Heidi; or
Suzanne nn
Suzie instead of any of them?