Reddit reviews The Belief Book

You might want to take a look at The Book of Gods or The Belief Book, both by David G. McAfee. I've read (well, skimmed...) the first and it's definitely aimed at that age range and seems like it's just what you're looking for.

This book does a great job:

The Belief Book by McAfee & Harrison

>What is belief and why is it so important? Where did it come from and what does it do? This book answers all of those questions and more! David G. McAfee, an author who studies religions, teamed up with writer and illustrator Chuck Harrison to create The Belief Book. No matter how old or how young you are, this easy-to-read book can help you learn more about religions and gods and beliefs in general. It will also teach you about something called The Scientific Method, which is how we learn new things about the world! By the time you're done reading you will know the answers to some of life's biggest questions, but more importantly you will see why your questions, and all questions for that matter, are so important. This book is the first in a series of books all about belief, gods, and religion. The fully illustrated and interactive Belief Book is for readers and thinkers of all ages, including kids and kids at heart.

A simple search on the error page resulted with this:

https://www.amazon.com/Belief-Book-David-G-McAfee/dp/1908675314/ref=sr_1_2?ie=UTF8&qid=1542124475&sr=8-2&keywords=chuck+Harrison

Username checks out! :P

Some of the books we use:

The Kids Book of World Religions

The Belief Book

Awkward Moments (Not Found In Your Average) Children's Bible Book Series

I'm going to order the Church of Satan Activity book for this holiday season. Only $5! Thanks /u/lifebeatmyass

Some ones I can think of offhand plus a few lists:

Me & Dog

http://www.goodreads.com/list/show/41547.Atheism_and_Religious_Disbelief_in_Children_s_Fiction

http://www.csicop.org/si/show/skeptical_books_for_children_and_young_adults

http://www.atheistrepublic.com/blog/karenloethen/books-your-skeptical-children

There Are Not Monsters Under Your Bed: A Storybook for Skeptical Thinkers

Maybe Right, Maybe Wrong

It Is Ok To Be A Godless Me

Humanism, What's That?: A Book for Curious Kids

I'm An Atheist And That's Ok

Older than The Stars

Our Family Tree: An Evolution Story

Star Stuff: Carl Sagan and the Mysteries of the Cosmos

Richard Dawkins’ The Magic of Reality

The Golden Rule

The Belief Book

http://parentingbeyondbelief.com/parents/?p=384

God Is Redundant

Here are some books you may find useful:

https://www.amazon.com/Belief-Book-David-G-McAfee/dp/1908675314

https://www.amazon.com/Book-Gods-David-G-McAfee/dp/1533066760

https://www.amazon.com/Relax-Its-Just-God-Religious/dp/1941932002

https://www.amazon.com/Parenting-Beyond-Belief-Raising-Religion/dp/0814437419

https://www.amazon.com/Raising-Freethinkers-Practical-Parenting-Beyond/dp/0814410960

You might consider talking about some other religions as well, to reinforce the idea that there are MANY different beliefs about what happens after we die (reincarnation, etc). Maybe check out a good kids book on world religions from the library and look through it together. You also might take a look at "The Belief Book" by David McAfee: http://www.amazon.com/The-Belief-Book-David-McAfee/dp/1908675314/

David G McAfee has this and apparently is good for kids, and has others especially useful for shooting down MIL as she probably thinks atheism is worse than Islam from how you describe her

https://www.amazon.co.uk/Belief-Book-David-G-McAfee/dp/1908675314

• The Belief Book
  
• The Book of Gods
  
• The Book of Religions
  
  ​

The Belief Book

http://www.amazon.com/The-Belief-Book-David-McAfee/dp/1908675314

Check this out

Having lived through similar from both sets of grandparents I cannot recommend the books by this author enough. Let them know about Christianity but also about every other religion out there .

The Belief Book https://www.amazon.com/dp/1908675314/ref=cm_sw_r_cp_api_i_Nr3ZCbSERR6QY