Two choices for distance - 6 miles roundtrip - includes wooden boardwalks, nice smooth pavement and uneven pavement (you have to ride on the street for short distances).
12 miles - this includes both sides of Route 5.
Because the bike paths are new(er) this is a very easy ride. A new waterside park opened earlier this month, complete w/a splash pad. Included in the 12 miles is a ride through Times Beach.
I have two extra bikes, if anyone needs to borrow. Both are 26".