Coyne (which usually went to Cain/Kane) is I think an Ulster Scots name - not Manx (the nearest here is Cayne which is a 17th C alternative spelling to Cain(e) which had displaced it by early 1700's) and would in my opinion be very unlikely as a rendering of Quine - there is no record I have of such a Silvester producing children by these names, no will, no bural record etc thus I suspect you are looking in the wrong place.