My wife and I spent nearly a week at Caroline's apartment and chose it primarily for it's location. We know Boston fairly well and the North End is hard to beat for its central location, its restaurants and cafes and easy access to public transportation. It can be bustling at the weekend but the apartment was always very quiet and peaceful.
Long Wharf is an easy ten minute walk from the apartment and for a change of pace you can take a ferry from there through the Harbor Islands to Hull or Hingham. You can also take a water taxi to Logan airport from the wharf - a very pleasant way to get to and from the airport.
Caroline was a gracious host and I'm sure you'll enjoy a stay at her apartment.