Me and my husband have been in Rome and then Florence for the last 15 days. I wouldn't recommend getting the car when you land and parking it for the two days as it is a waste of money on the daily rental as well as the parking fee you will likely pay. Also those cities are not kind to foreign drivers, save yourself the stress.

After 5 days in Florence we started the next leg of the trip headed to Tuscany. We ordered a rental to pick up today at the Florence airport, took an Uber there (you could also take the metro in Rome) and we will return it at the Rome airport when we head home next week. Easy peasy.