A day spent at Franklin Institute and to Chinatown in the evening.
< http://www2.fi.edu/
It has added many new sections and exhibits since I was last there in the 1980's.
Kids loved it and enjoyed seeing everything, including the Imax theater.
Mark and my son enjoyed the Flight simulator though, son said (Inside the simulator to dad) 'we don't have to do that again' after turning upside down a few times too many.