Despite his insightful comments and impeccable vocabulary, Linus van Pelt almost always carries his blue security blanket and is constantly taken advantage of by his older sister, Lucy. Atticus Shaffer would certainly be able to mumble insights, but, more importantly, he would also scream the perfect scream when Linus looses his temper.
As one of our favorite child actresses, we would like to hear Savannah Paige Rae voicing Lucy van Pelt. While she usually plays more sentimental and familial roles (e.g. in Parenthood), we're confident Paige Rae could transform her voice and become the Peanut's cynical, eight-year-old bully.
With her experience voicing a fur ball in Horton Hears a Who!, we think Joey King would be a perfect fit for Peppermint Patty. The rather oblivious and slightly ignorant character requires a voice that can be tailored to her considerably dumb moments. (Please remember: Peppermint Patty was unaware that Snoopy was a dog. We get the Goofy dog debate, but not Snoopy.)
Confession: we will bring in one adult, but only for the coveted role of Snoopy. Assuming next year's movie copies the original cartoons, Snoopy will not speak, but rather express himself through obscure noises. After his performance as WALL·E, we think Ben Burtt is fit for the job.
Charlie Brown's temperamental younger sister, Sally Brown, is rather obsessed with Linus. We can imagine Skai Jackson crying "My Sweet Baboo!" as Sally—clad in her pink dress—chases after Linus with his blue blanket.
He's a little crazy—some might even say raucous—on Modern Family, but we would love to see Nolan Gould as Charlie Brown. The actor has the ability to maintain a calm voice while also being quite quirky, perfect for the "wise" yet incredibly clumsy character.