For convenience, the Crowne Plaza right off Route 95 (801 Greenwich Ave Warwick, RI 02886, (401) 732-6000) is probably your best choice. It is within a mile of Route 95, easy to find, and about half way between CT and MA.
For a unique venue, you could rent the Rose Island Light House (http://www.roseislandlighthouse.org). Accessible by boat owned by Rose Island Lighthouse Foundation from Newport. Since it is a Bed and Breakfast some people could stay overnight. Unique and beautiful, but not as convenient as, say, Crowne Plaza.
For a place more accessible than the lighthouse, but more intimate than a Crowne Plaza there are a number of Bed and Breakfasts and smaller restaurants. I have attended events at Tower Bed and Breakfast in Narragansett RI (http://towerhousebandb.com). The facility is very nice and the owners do everything they can to help out.
For other venues in the Narragansett Area, I would recommend contacting the Chamber of Commerce (http://www.narragansettcoc.com/) and asking Deb for ideas. Deb has significant restaurant experience. I would also contact the Southern RI Chamber and ask for Elizabeth (http://www.skchamber.com) who also has significant restaurant experience.
In terms of activity at your event, if you would like a set of activities which are entertaining, fun, and teach us more about how we sense, perceive, learn, remember, make decisions and respond I'd be pleased to offer a version of my Education by Entertainment programs (contact information at: https://sites.google.com/site/educationbyentertainment/arranging-a-program).
Many thanks for asking.Ron
Ronald G. Shapiro, PhDEducation by Entertainment