5 days in Florence


New member
My spouse and I are visiting Italy for the first time from 6/8-23/2015. We have plan to visit:
3 days Venice
5 days Florence
5 days Rome and
3 days Naples
We would like to have a combination of sightseeing and discover surrounding vicinities specially in Florence and Naples. We are coming from paris with train and we have plan to get. 4 days euro train in Italy. We would like to know the following:
1. Is 4 days euro train is a good idea
2. Should we rent a car in Florence and Naples
3. We plan to book AirBnB for our entire trip. Is it a good idea?

We would be grateful for a comprehensive schedule, itinerary, suggestions that make our first trip a joyous one.