If you're going to be in southern Italy,don't miss Pompeii...or Capri.They're both fairly close to Naples.
Also note,southern Italy in the summer is hot,hot,HOT!
And humid!
We were in Naples a couple of years ago. In February! It was lovely. Didn't get to Pompeii, because we had spent ten days in Rome and I overdrew my husband's patience by spending too much time looking at what he refers to as "rubble". Next time for sure.
This trip will be Pisa, Cortuna, Bologna and Lucca. Can't wait!