Here's some excellent resources I know of...and a few my friends love... (and my list is more for listening than the music or performing part, I don't have a musical skill set other than to enjoy it a lot!)
A book in the Emmaus library with guiding principles (more for a choir)
....a majority of the book deals with what would be good for a children's choir but I liked it in the fact that it divided into Biblical Perspectives, Educational Perspectives, and Contemporary Challenges. It would help you think about music choices when there are so many, how do you choose the best?
by Connie Fortunato
Videos of songs that kids sing...
- Oh how I love Jesus....
- a whole list of songs with motions, sung acapella to familiar tunes...and I like her song card/picture idea for young ones! http://missionbibleclass.org/songs/
- another list... and some other links http://ministry-to-children.com/music/