Campania
If your kids like volcano's, southern Italy is the place to be. Along with Mt. Vesuvius, there are bubbling volcanic craters and mysterious grottos, and islands formed by volcano's. Boat trips to Ischia or Capri is fun for everyone in the family. At Pompeii, kids can travel back in time to see an amazingly preserved ancient Roman city. And there's always swimming in emerald waters and playing on sandy beaches.
Island of Ischia - Take a scenic boat trip to Ischia, the largest of the islands in the Bay of Naples. Spend the day relaxing on the long sandy beaches (Maronti is the longest), or in the thermal springs. Visit the dramatic Castello d'Ischia, a 14th century castle in the Spanish style, perched on a rocky promontory overlooking the sea.
Capri - It's a close hop from Naples over to the island of Capri. Ride the hydrofoil (big hit with kids) or take the ferry. From the Marina Grande, you can take a boat to Blue Grotto, or ride the funicular (tramway) up to the town of Capri. Walk out of town for great views or take the local bus between Marina Grande, Capri and Anacapri.
Amalfi Coast - The Amalfi Coast is famous for its vertiginous cliffs and spectacular scenery. There are good swimming beaches sprinkled up and down the coast. Most charge a fee for access to the beach. Visit the Emerald Grotto (Grotto dello Smeraldo) - you take an elevator down to the cavern and a boat ride through the green waters. Splurge on a submarine ride on the "Tritone" around Capri, exploring the underwater scenery.
Paestum - Paestum is a little bit of ancient Greece in Italy. Poseidonia was founded by the Greeks in the 6th century BC, later the Romans called it Paestum. Today Paestum has three lovely Doric temple with fat cigar-shaped columns to run around and lots of open space. Take a picnic. Paestum is also a beach resort - so spend some time relaxing at the seaside.