I went to college there at Northeastern University and know the town well! Lots of great things to do there.
North End for Italian food, followed by Mike's Pastries for dessert, if that's up your alley. If you like wicked pissa Clam Chowdah, Legal Seafood makes some of the best (served at inaugurations of most Presidents, or at least used to be).
If you want to do some walking/shopping, areas around the Prudential building, Newbury St, Boylston, is a good place for that.
Fenway tour is highly recommended. Best to see a game live there someday - only a couple parks that compare.
Samuel Adams tour is fun. Cheers bar is a fun place for a beer and pic, if you liked the show. Prudential top floor has a restaurant and bar - nice place to grab a bite and a drink and overlook the city.
Museums - MFA is incredible, Gardner is great also - huge art heist years and years ago that you may have heard of
https://www.gardnermuseum.org/about/isabella-stewart-gardnerFreedom trail is cool
The Granary Burying Ground in Massachusetts is the city of Boston's third-oldest cemetery, founded in 1660 and located on Tremont Street. It is the final resting place for many notable Revolutionary War-era patriots, including Paul Revere, the five victims of the Boston Massacre, and three signers of the Declaration of Independence: Samuel Adams, John Hancock, and Robert Treat Paine. The cemetery has 2,345 grave-markers, but historians estimate that as many as 5,000 people are buried in it.[1] The cemetery is adjacent to Park Street Church, behind the Boston Athenaeum and immediately across from Suffolk University Law School. It is a site on Boston's Freedom Trail.
Walk through Boston Public Garden/Common (you can do the Cheers thing, graveyard, and Freedom Trail all together since this is all centrally located)
Anthony's Pier 4 Cafe - Used to be one of the finer places to eat. Then it burned down. Not sure of the rebuild is as worthy, but it used to be one of the finer seafood joints in town.
Capital Grille was another favorite of a lot of folks I know. Marios also.
If you are driving around the outside of the city (Lexington as others mentioned) Walden Pond is a cool place to check off your list, if you or the bride liked Thoreau...just down the road from Lexington