Love Venice and Naples too..
my fathers family was actually born in a nearby town. We took the hydrofoil to Capri and walked around,had fantastic lunch,,but missed the Blue Grotto due to poor weather.As you know,,,Naples can have sort of a "rough" reputation,,but my limited Italian and looks?? may have helped me fit in and love it. We rented a car and explored Sorrento on our own,,on a sort of "roots" tour.But the driving is CRAZY...would nt do that again...
Venice,,LOVE LOVE LOVE it...there 2 days last June and used the people mover and vaparettos to get around.Went to some of the small islands...much less touristy.
Sorry you missed the Vatican,,,we actually SAW the pope,,from a great distance.Saw all the famous sites and even lit a candle for my father in a small private chapell.I m not even Catholic,,but was very impressed...
We always google tourism site in each town,,,then figure out what WE want to see.Even take shore excursions if a good deal.Also,,take a lot of HOHO buses.
Any particular questions,,let me know...will try to help...have FUN>