T.C.
First of all... make sure you take a picture of your little Picasso's art work! lol
Well, I decided to look up some other ways besides the Magic Eraser since I have had them remove more than just marker and stuff from my walls! I read that using a dryer sheet will remove crayons from the wall. OK... now I really feel like a bone-head since I decided to go and test it!
So, I took my daughters blue crayon and 1 Gain dryer sheet and WOW- it really worked!! I am sure any dryer sheet will work. I tried it on a few spots where we have different paint and it really does work on them all! And here I thought someone was smoking "stuff"! The only thing I did notice is on one area where I tried it the paint is more textured... I had to ball up the sheet and use a tiny bit of elbow grease to get in the "crevices" of the paint.
Good luck and blessings to you and your talented artist :)