I went back and had a look at your travel plans and I think you're doing yourselves a disservice by trying to get to Washington in only two days. It's over 1,000 miles from Little Rock to DC, so with only two days you really wouldn't have the time necessary to take scenic roads or make stops long enough to really enjoy any of the museums listed above. I would strongly advise adding another overnight stop on the way to DC

AZBuck