Unless you're talking about transportation into or out of the city, cars shouldn't really be a consideration.
Boston traffic sucks and looking for parking at the sort of venues the group would likely be visiting will be tedious, expensive, or impossible. As long as people are willing to pony up the $2.00 per trip for public transportation, that's your best bet by far.
i know driving in boston sucks, i live here
i was more asking because i believe people wanted to go to Salem