I can't help you with B&B's, we stayed at a hotel for one night on our way to the Cape, but we ate The Red Parrot and they had the best lobster bisque!! It's been three years and our family still raves about it!
We toured The Breakers and I believe the other two were The Elms & Rosecliff. I want to go back and tour everything, they are really incredible to see!

B&B: Francis Malbone House

Eats:

Nice: The Mooring, Clarke Cooke House, 22 Bowens, West Deck

Casual: Brick Alley, Red Parrot,

Funky Food/Lounges: 5th Element, Salvation Cafe

Mansions: Breakers is a must. Astors Beachwood if you'd like to see people dressed/acting like people of the period.

Check out

www.gonewport.com

for lots of info.

A second vote for Francis Malbone House for B & B

My favorite things:
If you have a car, the ocean drive/ ten mile drive
www.oceandrivenewport.com

Fav place for sunset: Castle Hill ( if not then, for some meal, cocktails, dinner, something - amazing view and sunset is lovely time)
www.castlehillinn.com

Other fav restaurants: 22 Bowen, Clark Cooke

Go to www.newportmansions.org
and read about each mansion to decide what appeals to you and to get a variety.
The Marble House is opulent, RoseCliff modeled after the Petite Trianon at Versailles, the Elms has great garden area while being smaller mansion, Astors Beechwood b/c of history, attachment to Titanic, etc, etc - so it is nice to get a mix and not see two similar ones - although from the Gilded Age, different ones have different styles and degrees of opulence in various ways

Consider adding to this mix the Newport Art Museum on Bellevue which was designed in 1862 by Richard Morris Hunt, and is one of the best examples of the American Stick Style architecture. Hunt also designed the Breakers, Marble House, and others.

Plus, it has nice exhibits and two other buildings VERY different architecture - I encourage you to at least check out their web page and also see what artists and exhibits will be there during your visit - the woodwork and inlay in this 'summer cottage' is gorgeous.

www.newportartmuseum.org

Things to consider:
The International Tennis Hall of Fame, even if not tennis fans, walk inside to see the horseshoe, etc and the museum itself is quite interesting

The Touro Synagogue- it is the oldest synagogue in the US and fabulous Georgian architecture (Harrison) and is a national historic site that is worth a visit - www.tourosynagogue.org

Cliff Walk
www.cliffwalk.com

Also, check out Newport Festivals, or events at the Newport Yachting Center, although by late Oct I think you will have even missed the Oktoberfest - but you can see if something else interesting is going on -

I think all these websites are right, or close enough for you to perhaps track down - I am not at home wtih all my usual info nearby, but still on my summer break, just checking in on Fodors for the first time in weeks but can never resist info on Newport or seconding a recommendation to Francis Malbone house -it is a gem

have fun !