Last year my wife Emily and I trailered our boat to the Cambridge launch ramp and sailed the Choptank River in September. The weather and winds were great and there was plenty of stuff to see and do. Including the maritime museum at St Michael's.
The Narragansett Bay including Newport and Penobscot Bay in Maine are other possibilities.

Best Regards
Jeff Smith
www.http://JeffSmithPhoto.Net
732-236-1368