There would have been guardianship papers for the children because their parents died when they were minors. They might mention their mother's death. I'm not sure if the Saline County Clerk of Circuit Court or the Saline County Clerk has these documents.
I think they're also at the Arkansas Archives, www.ark-ives.com/
. They won't loan the microfilm but they will copy a document.
The Saline County History & Heritage Society, www.schhs.us/collections/
has Saline County Obits & Death Notices 1823-1930.
I saw on another's family tree that Sarah's maiden name was Cobb and saw the marriage record online.
In 1870 two of the children are living with George & Nancy Cobb, Brown, Columbia, AR. Successful Searching!