Lesley might answer an e mail about this......address is on the site. A few of Child's own words about what he was collecting would probably do the trick. Ask your librarian if she could InterLibrary Loan Volume 1 of the "English and Scottish Popular Ballads" by Francis J. Child, and look in the introduction.
Lesley is the OnLine Child expert, could you use a quote from the site itsself?
Most of us here at the Mudcat are "amateur" musicologists, but Malcolm Douglas is pretty amazing at documenting things. I'll message him and ask him to check in on this.
Great idea for a project, by the way! Good Luck!