I don't know that I can help much. If the sampler was made in 1796 then it couldn't have been done by Mary Player wife of Joseph as she was born c. 1791 so would have been too young.
Joseph's mother or a sister could have been a Mary but I have not been able to trace his earlier family. He was born in Henbury, Glos. c. 1781. I have made a note and if I find out anything I'll get back to you.
Incidentally I only knew of 5 children for Joseph and Mary. I have Sarah, Martha, Ann, John and Maria. Do you know the other 3?
Regards
Moss