First of all, I go to Orlando pretty much at least one a year and, even considering you're coming from overseas, two weeks is a lot.
Lets turn the tables and assume I'm visiting the UK. If I were to want to travel from Plymouth to Aberdeen on my overseas trip, I would never go without seeing what is in between. I would get a British Railpass. Amtrak also has a railpass for overseas visitors. The fare is about the same as simply buying a one way ticket for anyone else. You're going to travel in the off season so prices are a bit lower and I would recommend an eastern 15-day pass. Leave Boston, but, rather than change trains in Washington, stay a few days and see the sights. Get on the train again and off in Savannah and enjoy the old south for a day or two. Get back on and continue to Miami and sit on the beach. Then take the train a few hours north to Orlando and spend a week at the parks. This itinerary also has the advantage, in addition to letting you see the country, of not having you spend the night on a train, which can be pretty uncomfortable unless you spring for a room of some sort.