Last summer, we piled the kids in the car and went on a normal-for-us trek across the globe, landing in historic Washington, D.C. If you've never been, it's a wonderful trip. The entire Smithsonian is free. Monuments. Science Museums. History museums. Arlington Cemetary. The Zoo. It's all amazingly, wondrously available with no entry charges. One of our must-do's on the trip was Arlington National Cemetery, to visit the Tomb of the Unknown Soldier. On the day we visited, rain was coming down in buckets (as some of my friends in the south say, it come up a flood!) and we...