My suggestion would be READ the books and discuss the ideas together. You don't need a guidebook. These are children's books, and they are NOT allegories, so nice and easy to enjoy.
Your family will get more out of them by enjoying them as stories, not being told they are Christian material. After you have finished the whole story of "The Lion..." will be the right time to ask the family what they noticed and so on.
Otherwise there are several useful commentary books which all have a chapter talking about how the Christian ideas are woven into the stories.
Enjoy them!