While in the Boston area and if you run into a rainy day, it is known to happen in New England, you may want to check out the Peabody Museum in Salem, MA which has some great exhibits of the China Trade era with the history of Clipper Ships.
http://www.pem.org/exhibitions/
Another beautiful spot for great views of the Atlantic Ocean is Halibut State Park.
http://www.mass.gov/dcr/parks/northeast/halb.htm This is located in Rockport, MA which is a artisan town with lots of shops located on the coast.
I love traveling route 1 up to Maine, traveling through NH is a treat since there is only a small portion of the state that is on the coast and there is miles of ocean views as you drive along. Portsmouth NH has some nice shops and restaurants and great views as you cross the river into Kittery Maine.
You will also find the Nubble Light, also known as Cape Neddick Light Station right up the road in York, ME
http://nubblelight.org/ which offers some great views and photograph opportunities.
Lots of great towns along the road but a place I love to visit is the Wells National Estuarine Research Reserve.
http://www.wellsreserve.org/ The reserve is located on the old Laudholm Farm which has miles of trails as well as miles of seashore to walk.
You certainly can enjoy the southern coast of Maine and do hope you have some good weather. My memory of New England is you can still have some brutal winter days in March as well as some comfortable days.
If you do have the time to head north of Portland, you may want to visit Booth Bay Harbor, a beautiful spot.
Good luck with your travels and do hope you find good weather and sunshine on your trip.
Note: If in Boston and the weather is more suited for indoor activities the Museum of Fine Arts is a nice place to visit, lots of exhibits and they do allow you to use you camera while in the museum.