Hi,
I didn't see your reply til now! To my knowledge, there are no Joseph P. Srader grandchildren. By 1880 all of Philip's children (as well as him) had changed their last name to Shrader. However, in the past year, I have found the parents info, as well as siblings of Philip who were all born in PA and many of them remained in Western PA. His brothers who had children were John b. 1813, Andrew C. b. 1830, William B. b. 1828, and possibly Jacob b. 1817. I don't know if Jacob had children or not. From census records I have not seen a Joseph P. Srader as a son of any of them, but I do not know about grandchildren.
Marcia