Today my father called to say that he and his sister had found copies of their father's birth and death certificates. That saves both time and hassle, especially since the birth certificate requires a court order in NY State. Now I only need to have court orders to amend the documents that need to be amended.
They also said that they were going to try to get a copy of their parents' marriage certificate. There was none in my aunt's records. But they will try to get one issued from the City of Buffalo or New York State. Fingers crossed.