I am Robert Justin Dunlavey, a first cousin of John Dunlavey (see his response in this thread), and have produced a website at http://dunlaveynj.home.att.net (note: no "www") in which I have included genealogical information I have been able to gather on my family (including Dunlavey) to date (including 70-odd descendants) (note: birth dates of living descendants are "privatized" in the geneaolgical report).
On the Dunlavey side, I've only been able to get back to Denis Dunlavy, my great-great grandfather (father of Robert, grandfather of Robert Joseph--my grandfather, and great grandfather of Justin---my father, who immigrated from Ireland (it is thought via Canada in the British army), lived in New York in the Elmira/Finger Lakes area, served in the US Army in the Civil War---in his '60s(!), and die in June 1877. He is the only Dunlavey ancestor who spelled the name "Dunlavy". He is buried in Mt. Olivet cemetary in Ithaca, NY. All his descendents (that I know of) spell the name "Dunlavey", and no one seems to have any idea of how, why or exactly when the change of spelling came about. I'm interested in finding the "Ireland connection" to reach back further in time.