Hauling opinions wanted. Help please.
 

In may I am riding from Pittsburgh Pa. to DC with my Uncle. I agreed to carry evrything. Wer'e staying in motels so no camping or cooking stuff. I have a 2000 Kona Fire Mountian with 13000 miles on it. no front eyelets. I do have a seatpost mounted rack that will take panniers, will it get to heavy? should I try to borrow/rent a trailer? Opinions please.

With hostel/motel style touring you can go ultralight, no need for a trailer. Shoes and towels seem to be the bulkiest items and easy to slim down.
I would suggest fitting a bolt-on rear rack to your bike and using 2 panniers. Seatpost clamp racks are pretty useless.
You can fit a bar-bar and a large carradice style saddlebag to your uncle's bike so he can take his personal stuff but you can carry all the tools.