Someone on one of the message boards I frequent posted a link to an article on Budget Travel Online that highlighted 15 places kids should visit before they're 15 years old.
The list is:
-Ellis Island Museum
-Lincoln Memorial
-Colonial Williamsburg
-Pearl Harbor
-Grand Canyon
-National Civil Rights Museum
-Redwoods National Park
-Gettysburg
-The Alamo
-Ground Zero
-Niagara Falls
-Freedom Trail
-Independence Hall
-Walt Disney World
I've been to 6 of these if you count Ground Zero before 9/11. I only visited 2 of the places listed before I was 15.
Quite an ambitious list, especially when you consider that you probably would visit any of these places much before your kids were 4 or 5. That's a lot of traveling to do in 10-11 years.
Good jumping off point, I think, though.