Well, it's possible, but I wouldn't recommend it. You don't have a full 12 hours, you've got to disembark, and u need to allow some buffer time getting back. No fun being left behind! The best train station in Pisa for the Leaning Tower complex is not the main central one, but the suburb one, Santa something, (plenty of net info). Short walk then to site entrance. IF you don't want to see anything but the Tower, then you might get away with it, and if you're there early you might escape the main throng of wretched African (mostly) hawkers and vendors of assorted bags, handbags and other tat. (not just Pisa, they're a pest at most big European tourist venues these days). Florence deserves some planning, but you could get church/museumed out, as there's masses of history, art and architecture to see. And leave time for a spot of lunch, and an ice-cream or three! If the kids are ok with all that history/art etc, good luck to you. IF you want to include the major gallery (Uffizi) be aware it's closed one day (Mon or Tues, forget which, and I see July 3 is a Tues, so better check); the crowds for the gallery are big, and it has a lot to see, so don't bank on going round in 15 mins!
I'd give Pisa a miss, interesting as the 'lean' is, and just do Florence, but do also be aware that July is likely to be extremely hot there, so that could a tiring day!
Try with http://en.wikipedia.org/wiki/Livorno for general info
http://www.webvisionitaly.com/category.php?id=241&ref_genre=&ref_item=349 this is a nice virtual tour with comments in english
this is a good one, too:
Ordered by the duke Alessandro dè Medici the old fortress was designed by Antonio da sangallo. The works for the construction of the fortress began in 1531 and continued until 1537.The walls of the fortress have a circumference of 500 metres;there are three raparts.On one of the two entrance doors is the coat of arms of Duke Alessandro.
Eretto tra il 1594 e il 1606 su progetto di Alessandro Pieroni, fu completato nel '700 con l'aggiunta delle cappelle e devastato nel 1943. La facciata, preceduta da un portico, è sormontata da una terrazza. All'interno, nella sola navata centrale le tele sul soffitto sono di Jacopo Ligozzi, dell'Empoli e del Passignano.
The hearth of the ancient town is the Duomo. Bernardo Buontalenti planned it at the centre of the pentagonof walls that surrounded the Leghorn of Renaissance times.
The best period to come to Livorno is during "Venice Effect", a holiday that takes place the first week of august: the historical centre, built on islands and full of canals, becomes a great tehatrical, musical, ethnical performing scene, and all the streets are full of stalls, little restaurants, lights and atmosphere.
Fondest memory: When I'm away I miss the incredible sunsets on the sea, full of orange, red and pink.
Fondest memory: Was arrival. This was the port of entry for most of the places last visited in February 1997. Didn't see much of the town as we went to Florence quickly. The story of that week is being created in the 1997 travelogue on my Florence page.
i guess there are almost as many dogs as people in Livorno
this is my friends' dog, his name is Franco
he is sooooo cooll