Hey!
From the jam front page:
you're free to write your game in a language other than English as long as it's equivalent to one thousand words
You can do whatever you want to your game after the deadline. It's yours! (And we can't stop you even if we wanted to LOL) However, it's always nice practice to leave the original jam version as a download option to leave it as a "record" of sorts.
Taking that into account, I'd suggest you focus on the English version and once the jam is over you add French and whatever other languages you want :)