My 1-yo. son and I are at MIT today, what should we do/see?

Go to the MIT museum! It's small enough to see in a few hours, and it's got robots! http://web.mit.edu/museum/

You'll probably see something interesting if you wander through the new Media Lab building, though it's difficult to predict what. :-)

I'm told there's a Lisp machine in a museum somewhere on campus. I'd find that interesting.