Here are links to online preview copies of two of Holling's books. You can read parts of the books online and look at some of the beautiful, full color illustrations.
Tree in the Trail ( Note: I have not read this book yet, but in browsing through it though it seems that Native American medicine men and superstition are portrayed in a positive light. I'd use caution with this book, though it is possible you may be able to edit it as you read it aloud. Again, I haven't read this one yet, so perhaps it is not a large part of the story. If you have read this book and have any input on this please leave a comment! It is worth looking at the pictures if nothing else! Please see my note at the end of this post on Holling's books.)
Pagoo (I haven't read this one either so I can't vouch for it 100%!)