Agree the GAP and C&O would seem out with those parameters.
Only thing I can think of is the D&L Canal Path from Yardley, PA. You could ride to New Hope, PA (12 miles), walk across the bridge to Lambertville, NJ and stay at the Lambertville Station hotel. (Mucho dinero.) Day 2 you could do a day ride out and back on the NJ side on the D&R path. Bulls Island Recreation Are is about 8 miles up river from Lambertville, so 16 round trip. Then back to Yardley on Day 3.
Maybe there are some options on the Erie Canal Path, but don’t know enough about it.