Believing comes by hearing. I believe that by hearing, memorizing, singing, and most of all praising God is a wonderful way for children to learn God's Word. The traditional hymns have some of the most memorable and beautiful phrasing, which describes who God is and that he loves all his children. Committing some of these phrases to memory will surely be a guide as children grow and face the challenges of life.
A must have if you are also getting the Kids' Hymnal because you most likely won't know all of the contemporary songs in the Kids' Hymnal. And if you can't read music (like me) then you'll definitely want the CDs. One thing about the recordings on the CDs, the tempo is a bit fast I think, but over-all, well done. Children's voices, not adult voices.