Paris France Optional +
The trolley tour of Boston, offered as an optional, is the best way to see the entire city. Take it at your own pace, but I would suggest stopping off at the USS Constitution and Fenway.
Winter is an excellent time to go to Europe. There are next to no lines for the museums, you can experience the cities like the locals do and everything is cheaper! Plus, Christmas and New Year's Eve in Europe are very special.
Do not travel with ONLY a credit card and/or debit card. Why? Cards can become demagnetized or lost….you should have some cash or traveler's checks to fall back on in case of an unfortunate inconvenience involving your plastic.