Trip to Boston suggestions

We have to go to Boston next week for a work conference, so we don't get to take the TD, but will have a few extra days and looking for sightseeing ideas. We have whalewatching boat trip scheduled and a few days in a B & B in marblehead, and a Duck Tour as part of the conference. We will have a car. We are both history buffs (of course, Boston!) as well as birders and wildlife. Any ideas?