Would you pronounce Janvier in the French way? Otherwise he'd be known as Jan, I imagine. Might or might not bug you.
Avril for a boy does seem like a stretch, but there was a South African rugby captain a long time ago (early 60s?) whose name was Avril Malan; apparently a huge bruiser of a bloke. So there are precedents ... and Avril on a boy seems to me much better than April on a girl!