Following what was listed in findagrave and on rootsweb, it is Henderson-1045. You don't need to enter the christening place (Scotland), but the birthplace should be Virginia, not North Carolina. He did die in North Carolina, however.
Both your findagrave and rootsweb sources list William Henderson (Henderson-10045) as William Henderson and Susan Florence Kearns, neither of which seem to be on wikitree.com as of yet.
William Henderson, husband of Susan Kearns, was supposedly the son of Alexander Henderson born in Scotland. This Alexander doesn't seem to be the Alexander Henderson who married Jeane Chessor though he too had a son named William Henderson. The birth year of Susan Kearns father-in-law is suspect as is the birth year of her husband William. I don't know whether or not his grandson had a middle name of Alexander to commemorate his grandfather Alexander Henderson. I've looked at it both ways, nevertheless.