How about the old Irish tune, "The Rights of Man?"
I'm just joking....actually the O'Carolan suggestion is a nice one, and I'll bet several could be played if the aisle is long---I've always been fond of "Lord Inchquin," which is think would make a lovely processional.
Also in many hymnals is a tune , "Lord of all hopefulness" which I believe was a Vaughn Williams arrangement of a traditional Irish tune. That one might be nice for congregational singing. HTF