Need some directions over to Waterfront in Newport
 

We will be in Newport on Thurs October 11 - (9 to 3) visiting from a cruise ship. We'd like to leave the cruise behind for a day and go to the area where we can hook up with the Oldport Marine Service. Maybe a trip on the Amazing Grace or catch a picnic at the Aloha Cafe and go to Ft Adams St Park for a picnic.
We want to spend the day around this area and maybe take a taxi over to the Point district to enjoy the old houses and their colors.

So, how do we get there from our ship? Is it walking distance, or can we get a taxi or bus from there?

Also, in that area, where is a good place to sit a while and eat, drink and dream?

The ship will anchor in the channel and you will tender into Newport. They let you off right in the center of the harbor, convenient to lots of stuff. There are lots of "excursions" you can book on your own. Just walk down the street to where they are "booking". The Point is within walking distance on the other side of the Information Center (it will be to the left when you get ashore).
There is a nice little park to have a picnic right next to the Point. There are plenty of places to pick up takeout food. (A Panera is nearby also). Or you could walk down Thames to Bowens Wharf and have a chowder at Black Pearl.

Lots of good things do to nearby.

I agree with all John said. Everything (except Fort Adams) is in walking distance. Given the relatively short time you have, I would not bother with going to Ft Adams for a picnic; it would give you a nice view of the Harbor but frankly as you enter and leave the harbor on your cruise ship (several stories up) you will have one of the best views of the Harbor and lower bay you could hope for anyway.
My family lives on the Point so I have spent a ton of time there. It is a great little neighborhood but there are just as many old historic homes closer to the wharf/waterfront (i.e. Historic Hill), so I am not sure given your time contraints you would be "missing something" if you did not walk over to the Point.

I read an article (Yankee Mag maybe?) that talked about the Seaman's Institute with the Chapel and Museum and some shop where a guy was doing scrimshaw. I remember thinking it sounded like a nice area to stroll around.

So I guess that is to the right of the visitor's center (which opens at 9:00)

We also are hoping to be bona fide leaf peepers. What is the chance around Newport this time in October? Or is it too soon to tell?

You will be there at approx peak foliage time. The best place to see would be along Bellvue Ave (where the mansions are). You could take the RIPTA (Rhode Island Public Transit) bus from the Transportation center that rings the Island and goes along the scenic Ocean Drive.
There is a shop that sells scrimshaw right along the waterfront (Bowens Wharf I think). There are numerous shops to strike your fancy there (also nice restaurants where you can sit outside and see the water.)