The Internet Medieval Sourcebook pages on the Children's Crusade.

Norman P. Zacour, 'The Children's Crusade', in A History of the Crusades, ed. Kenneth M. Setton, volume 2: The Later Crusades, 1189-1311, ed. Robert Lee Wolff and Harry W. Hazard (Madison, Milwaukee and London: University of Wisconsin Press, 1969), pp. 325-42, available online at: A History of the Crusades, ed. Kenneth Setton

The standard modern scholarly study of the Children's Crusade is Gary Dickson, The Children's Crusade: Medieval History, Modern Mythistory (Basingstoke and New York: Palgrave Macmillan, 2007).