I am arriving at Boston late Wednesday night and leaving Friday morning. What are the must-sees?

I am a big baseball fan, so I know Fenway is a must. I am a teacher and I will be traveling with my 8-yr old daughter (and grandma, too). There's not much time to spend in Boston (we're arriving from Stowe, VT), but I want to get as much of the city as I can (as well as Cambrige, if possible). What are the main sights to not miss (if it so happens I may never return... I'm from California). Thanks in advance. :)