When I did Heart of Italy last May the Sonya was booked as well for the days before the tour. We wound up at Hotel Selene which is just up in the next block from the Sonya (toward the Termini). The morning of the day the tour started we took our bags down to the Sonya. My SIL was ill and the Sonya was able to get her in to a room by about 10AM which was exceedingly nice of them. For the rest of us, they put our bags in our room as they became available during the day. The breakfast room and the actual breakfast at the Selene was a little better than the Sonya.
It was our first time to Rome as well. There were 5 of us so I knew a taxi from the airport wouldnt work, so I booked Rome Cabs. Their regular transports were full, so I booked their VIP tour and what a good idea that was! The driver was awesome and whizzed us around Rome for about an hour and half. I naively though it would help us get our bearings, lol. It did not but the tour was great! We did manage to go back and find one of the spots the driver showed us...the Aventine Keyhole.
You will have so much fun!