I noted the response to your posting on the Delaware forum that the family was Quaker so that may help narrow your search for Coppage graves.
I will pass along this entry from Dill's Kent County Cemetery Records. These graves are in Odd Fellows Cemetery located in Milford, DE. Your Ella and Edward are there. My parents are buried there as well.
Note that this is at the Kent / Sussex County line and you may want to extend your search into Sussex County.
Pinder, Edwin C. b. 3/5/1910, d. 6/16/1981 Husband of Mary J, Pinder; Add. 5 Lot 1734 Pinder, Ella C. b. 1880, d. 1954 Wife of G. Edward Pinder; Add. 5 Lot 1734 Pinder, G. Edward b. 1875, d. 1950 Husband of Ella C. Pinder; Add. 5 Lot 1734 Pinder, George R. b. 1917, d. 8/12/1974 Son of Ella C. & G. Edward Pinder; Add. 5 Lot 1734 Pinder, Gerald -No Dates Add. 3 Lot 1366 Pinder, Mary J. b. 1/7/1910, d. No Date Wife of Edwin C. Pinder; Add. 5 Lot 1734