I can see
Eponine being used anywhere. Gavroche is probably too strange to use in the English-speaking world. If you lived in a French community, though, I'd say go for it. For the record, I've loved
Eponine from the first time I heard it. It's one of those exotic names that stick in your head. I especially love the nn Eppy. Gavroche is a bit too...something...for me. Foreign, perhaps? It sounds more like a term than a name. Where did you first hear it, and what does it mean?