Oh my, frenchtown... I used to ride down there from my place in PA this past summer. The area is fantastic for cycling and your route looks good. As Ken said, just stay off the main roads. If you follow river road along the Delaware (29, 619, 627), you'll see tons of cyclists on the weekends.

NJ Bike Map is a great reference for planning:
http://www.njbikemap.com/njmap/maplocation.htm

If you feel up for a challenge, I know of a 19% grade hill right across the river on the PA side.