My 12-Year-Old Son Has Been Questioning God's Existence. Do You Know of Any Resources that Would Be Helpful to Share with Him? How About for Adults as Well?
I would recommend:
Children Demand a Verdict by Josh McDowell
Answers to Your Kid's Questions by Chuck Colson
Also, for adults:
Case for Faith by Lee Strobel
How Now Shall We Live? By Chuck Colson
Answers for Athiest, Agnostics & Other Thoughtful Skeptics by Calvin Beisner (this is out of print but can probably be purchased through http://www.addall.com/)