In your query you did not mention any date other than 1900. When did John and Mary Edwards die? If it was after 1930 there should be a death certificate. After 1913 there maybe a death certificate. Sadly if we were discussing white ancestors, I would suggest newspapers for obituaries.
I have found it is rare for slave owners to mention in bibles or to inscribe names on tombstones. If I was looking for slave names I would look in wills. If early wills included bedding, furniture, pots and pans you can bet they listed slaves by name. I read a will from the early 1800's that listed all slaves by first names and where they were to go even if they were to be freed. Good Luck.