Hi--hope you enjoy the East coast trip. Many great things to see & do.
Gettysburg---definitely do a haunted Gettysburg tour. There is also a museum (sorry the exact name escapes me now)--I think Nat'l Battlefield Museum--right across from the cemetary that Lincoln gave the Gettysburg speech at that is really good for a couple of hours. Our school takes our kids there every year on a field trip (battlefields, cemetary, museum). Also--the Gettysburg wax museum is amazing--about 20 scenes "acted" out--then a "movie"/3D sort of thing acted out at the end--It's a battle sort of scene laid out below you--you sit above and look down on different aspects of things happening. I hope some of these things make sense.
Places to eat: The Pub, the Dobbin House
Washington, DC--Also have taken many field trips there & used to live there. Things to see: Smithsonian--there are many of these. They are in walking distance of each other. The National Zoo is also nice. See the monuments: Washington, Lincoln, Jefferson, Vietnam Wall. All of these are relatively close to the smithsonians. (Plan to do a lot of walking!) There are also tour buses you can get on for a driving tour; I have never done one of these. Arlington Cemetary & the tomb of the unknown soldier is very moving--but a bit out of the way.
Places to eat: Phillips (if you like seafood--excellent, on the water)
Jamestown--Yes, another field trip...they have an amazing "village" set up--three parts--the Indian village, the ship, and the fort. Very cool--can be done in about 1/2 day. Then there is the Jamestown glassblowing which is nearby--neat to watch for a little while. If you do have more time--Colonial Williamsburg is nearby. It is set up to resemble what actually would have been happening in colonial times--the jobs the people would have had are explained/demonstrated. You can wander through stopping wherever you are interested.
Sorrythis was so long. Hope this helps you!