Again, many thanks. Following up on your advice about the IFHF web site, I did a search, myself, and found the marriage in Granard. That could be them. Their daughter, Anna, my wife's ggm, married a William Bell from Derry in New York. He was a Methodist, but all of the children, grandchildren, etc. in the family were baptised at an Episcopal Church in NYC, even after the family moved to Queens, which puzzled all of the descendents (even my wife was baptised there). But if Anna's parents were Church of Ireland, that might explain the attachment to the Episcopal Church in New York.
I will keep checking back on the IFHF site. I'm grateful to you for alerting me to its existence.