I have no doubt you will pair the art of Monet with the music of Debussy. I believe that the Impressionist movement began with Monet and his circle of friends in Paris--perhaps it was Manet who was the first to step out of line (?), but it was Monet's "Impression, Sunrise" which the style, "Impressionism" was named after. (Thanks, Wikipedia...) The musical movement came afterwards--a musical response to the artistic movement.
When people first started calling Debussy's music "impressionistic," they intended it as an insult, but clearly, he was not deterred from pursuing his own ideals. Like impressionist painters who used unconventional brush strokes, and tried to capture fleeting moments of light, rather than follow the methods of the old Dutch and Italian masters, Debussy broke the "rules" of structure and harmony and used "colors" of sound, as opposed to melodies, to create musical images. Because impressionism was born in Paris, you often hear it called "French Impressionism." I suspect Lily will love this unit!
Debussy's personal life was really quite tempestuous and sad, but he was saved by his daughter, "Chou-Chou" (a nickname, obviously), who was said to be the only person that he ever truly loved. He wrote for her a set of piano pieces (some of which I learned once upon a time), called, "Children's Corner," which are delightful for both children and adults. One portrays a circus elephant, another a shepherd playing on his pipe; there's one about a snow storm, and one about a dancing doll. The most famous is the "Golliwog's Cakewalk," which I'm sure you'll recognize. I think the kids would have fun trying to imagine the characters and scenery that Debussy depicts.
For more mature, orchestral works, I love "Prelude to the Afternoon of a Faun," and "La Mer." I'm not sure I know what a Faun is, but the music is magical. I've played "La Mer" a few times in various orchestras, and when I step out of myself and listen to the sounds around me, I can almost feel myself getting splashed with ocean spray.
Here is a great link Adrienne posted that she found on facebook. I love the artwork used as the cover of "La Mer," and I love that it was hanging in Debussy's own studio. I also love that the photo of Debussy and the "Great Wave" was taken by Igor Stravinsky. What wonderful connections!