Start with high-confidence art techniques for kids books, then narrow by subgenre or adjacent topics.
How to Draw People
Barbara Soloff Levy
Ultimate Origami Challenge Kit for Kids 8-12
Brian Soonho Yoon
Time to Make Art
Jeff Mack
National Geographic Kids Guide to Photography
Nancy Honovich
Easy Space Origami
Christopher L. Harbo
Super Simple Sumi-e
Yvonne Palka
Discovering Great Artists
MaryAnn F Kohl, Kim Solga
13 Art Techniques Children Should Know
Angela Wenzel