Send me a picture of your kid and I'll draw him. This shows a step-by-step demonstration starting with the photographs, then the first sketches, to the final cartoony version. Start by just sketching from the photo, sort, of realistic, to get warmed up, and to know the subject. Next step, try to cartoon-ize a little, caricature as you go. Layout out your final composition with light blue pencil, adding, details in order of importance. Before applying the marker color remember to erase most of the pencil so as to avoid smearing.
All these shots are from F.W. Murnau's Faust, 1926. This movie is one of the finest examples of art direction and composition in cinematic history. Disney's Night on Bald Mountain sequence in Fantasia borrowed heavily from Faust. I strongly recommend seeing this if you can get it on dvd. Murnau also directed Nosferatu and Sunrise. Sunrise is maybe the most brilliant movie ever filmed. You have to see it if you love movies.