Overall I think they're childish, but as I get older I find myself getting more whimsical in many ways. But besides the face emojis, there are so many others that you can use for humor or to get a point across. Avoid smiles, winks, etc. Most guys here will tell you that TEXTING IS ONLY FOR SETTING UP A DATE. To each his own I say. Just put yourself in her shoes, or better yet, imagine she is showing your messages to her girl friends before sending. Less is more...
On the flip side, be advised that emojis from girls can be fool's gold. They all send smiles, kisses, hearts, etc. Doesn't mean much at all.