Boston, Massachusetts is an old city (by American standards) and offers a lot of beautiful cultural and historical things to see (many of which can be enjoyed without spending a dime).
Visit a museum. The Museum of Fine Arts Boston is free (admission by voluntary donation) on Wednesday evenings. The public can also attend for free on scheduled Open House days (see museum calendar). Other museums in Boston with free days include the Art Complex Museum, Children’s Museum, MIT Museum, Bad Art Museum, Boston University Art Gallery, and the Institute of Contemporary Art.
Go for a picnic or stroll in one of the many lush parks that make up the Emerald necklace. This park system was created in the late 1800s to compete with Central Park of New York City.
Walk the Freedom Trail. This 2.5 mile red line guides you to over 16 sites of historical significance. Marvel at old churches, statues, meetinghouses, burial grounds and more while learning about events that played a key role in making The United States the democracy it is.
Tour the USS Constitution which is the world’s oldest commissioned warship afloat. Receive a free guided tour from a U.S. active duty sailor. Be advised, adults must show valid federal or state photo I.D. or Passport.
Explore the final frontier at Boston University Observatory. Views of the night sky through binoculars and telescopes are free to the public on Wed evenings (weather permitting). If the sky looks cloudy, call ahead an hour in advance to see if the observatory will be open.
Enjoy some free entertainment outside Fanueil Hall. Street performers of all kinds (singers, dancers, jugglers,etc…) display their talents to the crowds that gather here.
Play in a playground. It almost seems possible to me to tour Boston by hopping from playground to playground. A notable one is the Tadpole Playground with adjacent Frog Pond in the Boston Commons.
As you can see, the city of Boston, Massachusetts has a lot to offer your family, and you don’t have to pay much (if any) to experience it.