I went carless in May 2014 and it's been great. DC has decent mass transit, lots of car sharing (Zipcar, Enterprise and Car2gos) and there's an Avis car rental 4 blocks from my house. Before I gave up the car, I spent two months logging each trip (what it was for, how long etc) to know exactly how often I used the car and how much it was costing me to own it. (Backstory - I had bought my first NEW car ever in 2012 - face punch I know. Not only that but I financed it - double face punch! But since I rarely drove it, it was in fantastic shape with low mileage and I got a great price when I sold it. Paid off the lien and had $5000 left over to invest. )
It works for me because I live and work in a pretty small city. I admit, I occasionally miss being able to jump in the car and go somewhere on a whim. I do think it would be more challenging to go carless with kids - and with those Boston winters! You might want to do a dry run before giving it up. And run the numbers - if you own the car outright, it might be worth keeping it. When I actually did the math, keeping my car didn't make sense. YMMV, as they say!