We took the Pendolino fast train from Rome to Florence. I don't remember any stops and recall a elevator in the station if needed. Beware when arriving at Florence that the locals know to run out and get the few taxis waiting for the train.

In Rome, try staying at one of the hotels in the Via Veneto area. They are more expensive but well located for first time visitors and are more likely to have amenities for wheelchairs. There are plenty of good restaurants just out side of the major hotels.

You don't have to see all the historical sites to enjoy Rome. Definitely go to the Campo di Fiori, especially during the weekends. There are loads of things to see and do and it's nice and flat to wheel around in. If you feel adventurous, there is an electric bus that goes down the Via Veneto and goes right into the Fiori and runs late on the weekends. Remember where it drops you off and that should be the pickup area. I don't remember if it has wheelchair access but Italy is very progressive and I bet it has that feature. The electric bus is also less crowded.

Peter in the Bay Area