Re: RALPH PARTRIDGE/PATIENCE/ELIZABETH PARTRIDGE/WILLIAM KEMP/THOMAS THATCHER
This is probably a little late for your trip, but Ralph is most likely buried in the Duxbury Cemetery near the site of the First Church. There is no marker for his grave, per se, but there is a memorial stone at the site of the first church with his name.
Not sure about Patience. As for Elizabeth, I'm not sure where she is buried, but I presume it is in Weymouth.