Javier I like. Janvier not so much. (prn'd totally differently, I know) With Americans often being more familiar with Span. than Fr., I suspect
Javier would also have a better chance of being prn'd correctly.
Avril should be left on a girl... lumping
Avril on a boy is pretty much inviting hassles of people seeing the name and assuming girl and constantly having to explain to people why he has a girls' name.
Plus too many month names in the same fam can look kinda tacky. Some month names on their own even look tacky on a person imo.
May is fine on a girl and despite not liking them,
Augustus and
Julius or
Julian and
June can also be acceptable names on people. A little girl named
Avril or
April would be nice... then maybe something you can associate w/ a month on a boy w/out being outright obvious about it. The other month names just seem a little strange on people. Then again, I also find En. days of the week as tacky names for people.