My suggestion for Rome would be an Airbnb or similar apartment rental. With that many people in the group, it's nice to stay together. Where you stay really depends on what you want to do, but since you mentioned the ghetto area, the areas near piazza navona, campo de fiori, or the part of trastevere right by ponte garibaldi would be good choices - I'd probably pick the last one. The other areas around the ghetto that I'd avoid are the area near largo di torre argentina and piazza venezia. They're fine to visit, but they tend to be high traffic areas with a ton of people.

For Tuscany, if you haven't been to Florence, I'd stay there versus the countryside. I've spent good chunks of december in Florence and it's always really nice.