Re: John McMahon 1784
I've just discovered that Deborah did not go to TN after John died.www.binnsgenealogy.com has the 1790 and 1800 reconstructed censuses (tax lists) online for free.They both show Deborah still in Augusta County. I purchased the Binns CD of Augusta tax lists from 1782-1795 and it shows Deborah in each list from 1785 to 1795.
In addition, Chronicles of the Scotch-Irish has two entries showing Deborah giving consent in 1791 and 1792 for the marriages of her youngest daughters.So, she either did not travel with the Shields family (my vote) or only took a very short trip and returned to Augusta.
I'm quite certain that John was buried in Augusta in 1783 but I do not have any information about where his grave would be.
I do have more detail on the tax lists and Chalkey, but am too tired right now to look it all up.