neither of those sites are particularly helpful, at least from what i've been able to find on them... i'm planning on doing the same thing with my gf since flights are too expensive and gas is too ridiculous to deal with a rental car for a vacation. we're headed out to montauk with a day or two of rest in the bay shore / fire island area.
if you go to www.transalt.org
and check under maps, there are suffolk and norfolk co maps, but they're all on different pages, and i'd recommend ordering one from the ny dot to have handy and for planning. go to a bike store and get the nyc map to find out how to leave the city.
i'd be interested to know if anyone has any suggestions of places (cheap!) to stay in either of those places, or particularly good routes to take... it would almost be possible to do a good stretch of it on the beach roads on the south shore, but some of the barrier islands (likejones beach) don't allow bikes, which is frustrating...