Reddit reviews Activities for Building Character and Social-Emotional Learning Grades 6–8 (Free Spirit Professional™)

Tough age, especially for boys. Some could be a tough sell to your TBM wife - ease into it and tread lightly, being careful to pick safe-sounding books. You may have to check the age some of these recommendation apply to. You may also want to go through some of the books geared towards younger kids if they need more foundation. Use the library!

Let your kids pick a subject they are interested in and do a library trip.

https://www.amazon.com/Maybe-Yes-No-Dan-Barker/dp/0879756071

See the "Customers Who Bought This Item Also Bought" recommendations for a bunch more possibilities.

A list found on Reddit:

https://www.reddit.com/r/atheism/comments/436gdu/my_book_list_of_books_for_children_of_various/

More from another site:

http://overthecuckoonest.blogspot.com/2014/08/atheist-mama-whats-your-secular.html

Another promising looking one and the related books:

https://www.amazon.com/Activities-Building-Character-Social-Emotional-Learning/dp/1575423944/ref=pd_sim_14_20?_encoding=UTF8&psc=1&refRID=MAARJ6YHJN9HC15SQZ7P

A List and lists of lists at the bottom:

http://atheistscholar.org/filmsandbooks/parentschildren.aspx