I can't really add a lot more to the great advice you've already gotten, but I seem to remember that the Pope only has public audience on Weds. (and if he's in town). There's also a cool looking bug museum in Rome. I was SO disappointed when we showed up with the kids to look and it was closed. Being vacation and all we didn't realize it was Sunday :closedeyes:
We had the 6kids with us - 16 down to 3. We went easy on the museums and Churches. Kids like the Catacombs and the Colosseum. They also really loved the park in Rome - darn, I can't remember the name. The kids loved it because they could climb the trees there. It was a great place for them to run around and burn off steam.
Venice was our favorite city and the kids loved it too. We went to Murano for a day trip. The kids loved taking the water buses around Venice.
Cinque Terre was absolutely wonderful. Do try to go if you can. It was perfect for the kids. Such lovely vistas and a nice long leisurely stroll down the coast. We stopped at one or two of the towns and bought food at the local shops (cheese, bread and sodas) to eat along the way. Perfect. Local Italians are very proud of their local cheese. Very proud...and I was happy to oblige them.