A very tacky name in Japanese. Anybody well acquainted with Japanese culture would also recognize "Hanako" as the infamous girl ghost who haunts school toilets for some reason or other. In other words, though the explanation "flower child" sounds pretty, it's really not the smartest of things to name your child.
This name is so out of fashion in Japan it's considered a joke name. It's because of Hanako the toilet ghost - plus "ko" names are old hat now. Plus it's kind of a stereotypical name for Japanese characters in American media, kinda like Pierre is for French characters. Not totally unusable, but it might be better to skip this one.