Washington, D.C. is a must see for every American family. There are numerous tour companies to help you see many sites efficiently. Your U.S. Representative or U.S. Senator can help you with tours of the U.S. Capitol and the White House. The White House tickets are much more difficult to secure than they once were, but it's worth the effort. Of course, your family could easily spend a week just on the national mall going through the Smithsonian Institution museums.
Our family has really enjoyed Historic Williamsburg in Williamsburg, Virgina. It is close to historic Jamestowne and other historic sites and attractions on the James River. Richmond, Virginia and several Civil War attractions are in the area as well.
As you travel north, and get to Philadelphia and Boston, there are multiple options to please the history buffs in your family. All of these cities have other entertainment offerings as well. You do not need to immerse yourself in historic touring. There are theme parks, shopping, excellent dining, recreational areas and other ways to relax and enjoy your vacation.