To be clear here, the very best thing you could do for your surname and your blood line is to have your 83 year old cousin tested as soon as you can order a YDNA test from Family Tree DNA.Period.
Order a test kit from FTDNA for as many markers as you can afford, get his YDNA stored by at least taking the minimum test, FTDNA stores sample for 25 years (long after your last surviving McKee male kin is gone most likely)I am told by their ads.I am not sure of your age but you would be able to test any time thru Relative Finder or Family Finder even though your surname is not McKee you could still later work to match your 83 year old cousin if you needed or wanted to thru your mtDNA and autosomal DNA that you get from your McKee surnamed mother.You only have this time with him now for the current method of extracting YDNA for genealogy.
I will post this so as to more strongly emphasize that statement.
Check out the McKee NC-Penn group on the McKee Group page at FTDNA.My husband is kit 127187.I can discuss this in some detail but not on public forum for the sake of the privacy of the other kit owners who may or may not wish their McKee lineage discussed in public.
I would also suggest you post any questions you have about the usefulness of testing your 83 cousin asap on the RootsWeb Genealogy-L where the pros of both science and genealogy post.
I will send the links to your email address you have for this message.
Again, thanks so much for a serious input on this issue of the YDNA...............we can do no more or better for our ancient ancestors than to do these tests.