In order:Eponine - I've liked this name for a while but I can't say why. Elain - Nice name but the Seinfeld reference puts me off. Kestrel - I hate nature names.
Les Miserables is one of my favorite musicals so I have to go with Eponine. I am usually partial to French names anyway. Kestrel is ok though, and I like Elain but not that spelling.
Eponine. I love Elain. I'm not too fond of Kestrel (it makes me think of Kessel from Star Wars). Eponine has an exotic feel to it, and the sound of the name itself is particularly attractive to me.
Elain. Eponine just doesn't click with me, although it's fine, and Kestrel reminds me of Thestrel (creatures in Harry Potter). Elain, however, has the perfect little lilt. (: