I agree with your list, except I would add Glacier NP to it.
Your kids are a good age to really appreciate DC. Make them take a history book so they can look things up. And take them to Arlington FIRST so they have some concept of the sacrifices involved.
Get a good guide book like Fodor's before you go. It tells all the Metro stops closest to the monuments and attractions. Read up on navigating the Metro. It's really easy, even for a country girl like me.
For DC, don't try to drive in the city. Stay at Cherry Hill RV park, and you can get on a bus to the Metro stop and never need to move your vehicle.
