If your family likes electronics you might consider going to the Sony Showroom in Ginza:

http://www.sonybuilding.jp/e/index.html

Although it's not the top site in Tokyo, it is interesting for 1-2 hours. Ginza is one subway stop away from Tokyo station, which can be reached directly from the airport via the Narita airport express. Here's the webpage on that (it's probably in the other threads as well):

http://www.jreast.co.jp/e/nex/index.html