Couple suggestions might include:
Visit / tour the Harbor Islands? Supposed to be great weather.
Boston Harbor Islands Trip Planner | Tour Lighthouses | Boston Harbor Islands
Larz Anderson Auto Museum
Just looked - German Car Day is this Sunday
http://www.larzanderson.org/Topics/Topic.cfm?TopicName=Home&CFID=1285135&CFTOKEN=66765475
Not sure what the good night spots are....