Other books- you may be lucky enough to have in your library North Carolina Folklore, in 7 volumes, Frank C. Brown Collection, which really covers a lot of territory. Almost as good and more easily available is Vance Randolph's Ozark Folksongs (4 vol., but the one vol. abridgement by Norm Cohen, in paperback, is excellent. Many of the "Appalachian" ballads are here as well.
The nine to eleven year olds are certainly old enough to get great fun out of the murder ballads. Or trace the story and history of "East Virginia" to the old British Isles ballads "Awake, ye drowsy sleeper," many versions, many posted in this website, with bloody daggars and other things of interest to kids; threads 35233 and 50807. East VA and East VA
When I was in grade school, my outside reading included everything I could find on vampires and sorcery, but not many songs about these topics. Now I guess they all have read the Harry Potter stuff, which is very mild.