Do you have dates for the children, and/or information on them? I am searching for Margaret Black, m. Henry Clark (he was b. 1745, d. 1822 in Clarksville, PA). They had a daughter Mary Custen Clark, b. Feb. 11, 1783 in Philadelphia, PA.
Could this Margaret by any chance be the one in your list? I know it is a long shot, but the areas and dates are closer than anything I have found so far.