+1 for this. Been a couple of times before too and there's lots to see and learn, like how standard units of measurement are no longer based on samples held in vaults in London and Paris but based on fundamental physical principles like quantities of atoms or their radiation. (A kilo of pure silicon is very pretty incidentally.) There are anechoic chambers where you might find your ears playing tricks on you, and RF versions for measuring the efficiency of aerials and the radiation from mobile devices. And a computer history section where I've been found showing groups of schoolchildren how to enter a computer program using a manual card punch. They also give some lectures on their core subjects like the principles of accuracy but don't seem to be doing that this time.
Plus there are several decent pubs in the vicinity if we wanted to make it a group outing.