The show opens on September 19, this Friday, and runs through January 4. It features, according to the September 1 New Yorker (pae 46, but not online), 175 works (mostly watercolors, evidently) by Jean de Brunhoff and his son Laurent, who took over the series after his father's death in 1937. It includes a draft of Laurent's first such effort, Babar et Ce Coquin d'Arthur, and a number of public events: a lecture about the French imagination by Adam Gopnik on November 6 and, even more exciting, an illustrated lecture by curator Christine Nelson on November 21. There's a great deal of information, and some images, on the museum's website. This is an exhibit that is absolutely not to be missed; I think I'll wait until October, though, so I can also catch the only surviving manuscript of Paradise Lost. (Go in September to see some excellent early Bibles and prayer books.)
Babar, of course, is one of children's literature's greatest figures, so I won't add any effusive commentary here. He first appeared in 1931 in the book Histoire de Babar, le Petit Elephant.