To wit, I'm seeking a French equivalent of Wheelock's Latin.
I have used "Cornélie, ou le latin sans pleurs", by Salomon Reinach (1912), and liked it. This may be older than you were looking for. But if I remember Wheelock rightly, I think Reinach has a similar jaunty, chatty tone and an emphasis on reading short, typically edifying, passages. It's available online through the Bibliothèque nationale de France.
He wrote a similar book for Greek - "Eulalie, ou le grec sans larmes" (1911) - also available via the BnF site.
I can't say whether it's trustworthy or not, and it is quite old, but one French book that aims to introduce its reader to Latin is Nouvelle Méthode Pour Apprendre Facilement La Langue Latine: Contenant Les Regles Des Genres, Des Déclinaisons, Des Préterits, de la Syntaxe, de la Quantité, & des Accens Latins, mises en françois avec un ordre très-clair & très-abregé. You can view the 1761 edition for free via Google Books.
I found it of use when I was looking for information about the declension of the noun Pascha.