After reading all the advice, I decided to visit Florence while I was in Rome instead. We rented a car in Rome and took off to Florence - what a lovely city. We spent the entire day there, saw all the sights. And after all my queries about trains, we did not even go to Pisa. My 11 year old was just too tired. We did come across quite a few people however who had taken the train from Livorno to Florence. The train station is really very convenient for visiting all the sites. Given the possibility of train strikes at a moment's notice in Italy, give yourselves lots of time to return to Livorno. Cheers.