Believe it or not,
Lacey was originally a male given name (it went place name -> surname -> male given name -> female given name).
Because it's seen as exclusively female nowadays, I wouldn't use it for a boy. But my prejudice against male names being used for girls prevents me from using it for a boy, unless it's a mn. So basically I wouldn't use it for either sex, though I do like the look and sound.
I wouldn't hesitate to use
Lacy for a girl, though probably only as a mn because I see
Lacy as a somewhat "out there" word name.
Miranda

Proud adopter of 15 punctuation marks; see my profile for their names.