I am from Boston. Lucky you - Boston at that time of year is amazingly beautiful and usually comfortable weather. I strongly recommend you do the Duck Boat Tour - it takes about two hours, everyone who does one has a blast on it (even us locals), and it will give you the basic overview of the city and its history. Downtown Boston is pretty safe to explore on your own during the day, so after the duck tour, walk back and visit some of the sights on the Freedom Trail, get some chowdah and a beaah in Quincy Market, walk across the Rose Kennedy Greenway to the North End for some gelato, a cappuccino or a cannoli, take a swan boat ride in the Boston Public Gardens ($1.50 last time I checked - priceless!), walk a bit of Newbury Street and visit the galleries. Quincy Market and Faneuil Hall are pretty close to the cruise terminal - maybe a 10 minute walk, but you can catch a taxi back, too. There are plenty of photo opps near the waterfront - the breathtaking skyline, boats, etc. If you are looking for some Bohemian adventure, board the Red Line at Park Street Station in Boston Common for a 5 minute ride to Harvard Square in Cambridge - nose ring optional. You will love it and have a great time.