My friend Dale Tolmasoff has a delightful children's book coming out this summer with Crossway, entitled This Is No Fairy Tale. You can browse the book at Crossway's site and read John Piper's foreword for it.
Dale, by the way, is a former Jehovah's Witness, whose life has been wonderfully transformed by the grace and truth of Christ. Crossway has also published Dale's gospel tract for JW's: Who's Knocking at Your Door? which you may want to consider getting in order to prepare for, well, the next time they are knocking at your door!