I have visited Boston.... in the winter... but it was a neat city to visit. A bit tricky to drive around in Boston, but I enjoyed myself.
I am going to throw my two cents in for Williamsburg. It is close to Virginia Beach so you have the Ocean, and there is a tone of things to visit and do. They have a very family friendly hotel there call Great Wolf Lodge... it has an indoor water park inside the hotel! Colonial Williamsburg a neat place to visit, they always have lots of activities going on, and because it is a working colonial town, there is always neat demonstrations of how things were done back in the day. I like the blacksmith shop and the reinactments. They usually fire a few cannons too which is really neat. There is also an outlet mall and the Williamsburg Pottery is neat to visit as well.
Tom