My wife and kids thoroughly enjoyed themselves, and I was pleased by the tourist segments in which I participated. Philadelphias historic district is impressive, with all sorts of interesting and entertaining programming, thanks in large part to this organization. I liked the National Constitution Center well enough, as did the younger Knippenbergs, though dad and kids presumably had different interests and capacities for appreciating the exhibits.
One last point: in the historic district, ordinary Philadelphians were consistently friendly and helpful, one of them explaining to my wife that he tries harder because his city all too often gets overlooked as a tourist destination because of New York, Washington, and even Boston. I dont know how widespread the attitude is ("the plural of anecdote is not data"), but wed go back and recommend the experience to others.