We are learning about Greek Mythology right now and the girls have taken off like wild fire. It's ridiculously fun to see. We are reading a ton, and have started the Percy Jackson series, but this book, Amazing Greek Myths of Wonder and Blunders, by Michael Townsend is what has them riveted at the moment. It's very funny and the drawings are even funnier—it appeals to their absurdist sense of humor and love of comics so much. It's a great first book for them on this topic—the short versions of the stories introduce them to Gods and Goddesses that they can have in their back pocket as we go on. It is perfect for all 3 of them, 6-11.
This site has been keeping Sadie busy for reference, she's drawing all the Greek Goddesses right now. I have so many other books to recommend on this topic, but I had to post about this one right away.