Every carrier has a different policy and different fees and most differentiate between class of service, number of pets permitted in the cabin and number of pets per passenger.
As a starting point, take a look at each carrier's website and take some notes on its pet policies.
Then (or perhaps even first), review Italy's policies for pets with careful attention to vaccinations, quarantine and the like.
With multiple pets, you may well want to work with a professional service which can manage this for you. It will be expensive, but it is a system with little tolerance and if not done absolutely correctly, means a lot of hassle to unwind.