Good Morning Charles,
Your family tradition is correct but not because of the Clan Cranstoun. Since I posted this message I've done a lot more research and found that the Cranney history actually began with the Sept MacCrain of the Clan Donald. I have a web site that I've put this information on if you would like to view it:
http://www.geocities.com/reginacranney/
Also, did you William MacCranney (or a descendent) end up in Massachusertes? I found that name while doing my research.
Regina Cranney