Still Searching for Peter McKee

Mocavo sent me an email about more records being added so I decided to do a search.  I am still searching for my paternal great great grandfather, Peter McKee.  His son, my great grandfather, William F. McKee is buried in a small town cemetary near Monticello, Illinois.  When I visited the grave site there wasn't a death date on the stone.  I asked my dad and he said it was 1952 or 1954.  I ordered William's death certificate and found out it was 1952.  Also, on the certificate was his mother's and father's name which I didn't have.  They were Peter McKee and Emma Perkens McKee.  And the line stops there.  I have search Ancestry, Genealogy Bank, google, Family Search, and now Mocavo but haven't found them.  Mocavo had a ton of hits and I didn't have time to look at every one.  I plan on revisiting that search soon.