I have lived in/around Boston for 27 years and I highly suggest going to Landsdowne Street near Kenmore Square to have a few drinks and shoot some pool at Jillians or there is also a slew of clubs there. You could also go to Fanuiel Hall for the day and hang out and when it gets night visit some night stops like The Rack or The Black Rose which are great little watering holes,
For shopping make sure to hit downtown boston (chinatown) around washington street and you can take a quick cab ride/train/walk to Newbury Street which has a ton of cool stores for the girls, niketown, food etc.
For attractions there is always The Aquarium, Duck Tours are cool, stagecoach ride around boston, Museum OF Science with IMAX (shopping at the galleria is also a 5 min walk from there but nothing like downtown/newbury street)
Oops almost forgot the north end if you like italian food and just a cool place to hang out for a while.
It really all depends about what you like, if you give me some idea of what you guys enjoy I can help you out a little more.