We're thinking of travelling to New York and surrounding areas for 2 weeks in August. We would like to spend a few days in New York City, and then travel around a bit. My husband would like to see the Smithsonian, which means we'll plan to be Washingtion DC. What else could you recommend to plan into our itinerary that's worth seeing? Is there a big amusement park in that area for our 16 year old son? Thanks!