In my opinion Ben's chili bowl has some good chili-dogs, but probably not worth visiting unless you really like chili-dogs. every time i go there its usually on the way home from a bar at 1am and its packed full of other drunks which can be entertaining. if you want good tasting food that might have consequences in your stomach then i suggest going to eat some Ethiopian food. there are a few nice places but i usually go to dukem cafe.
Also if you take in a nationals game you can get some ben's food there too.
Also did not mention earlier that you can rent kayaks and canoes at a few different places around DC. i would suggest renting something around georgetown and paddling around the Jefferson memorial. Dont fall in the anocostia river, The Potomac is okay.