I just want to say I appreciate what you are doing with 4-H. It's really an important thing. Thank you.
To be honest, the best basic book I've read is "Trouble Shooting" by Gabby Franco. It is, literally, a basic shooting guide for "dummies". It goes through all the basics of grip, stance, trigger pull, etc. And I'm not sure if it would work for you but, there are also basic exercises at the end of each chapter. I say it may not work because it involves various homework in the way of stance practice, dry and live firing and so on.
You can get a copy on Amazon for about $25.00 +-. Or if you're close enough, I might be able to loan you mine if you want to look through it to see it it'll work for ya.