Tuscany and Rome

Actually u could be very busy with staying in the 2 cities. But if u must then take a bus from Florence to walkable Siena about 1 hr ride. For Rome I would simply stay. U need more time to leave rome and return..

This is hardly enough time to see Florence and Rome. You don't have time for day trips. You will spend most of your time traveling-2 nights=1 full day in Florence, 2 full days in Rome. If you want to go to Cinque Terra, just skip Florence and spend the night there.

By "day trips" do you mean things to see & do during the day in each of the two cities? Because any good guide book will list the main sights; your challenge will be narrowing the list down to what you can fit in with so few days. As a previous comment said, if you want to go to Cinque Terre then skip Florence -- you don't have enough time to do both. And the idea of taking day trips out of these cities when you've just arrived doesn't make sense.

I found a page with a possible itinerary, take a look... maybe it's useful to you: https://www.visitflorence.com/itineraries-in-florence/two-days-in-florence.html

We will be in Florence for 2 nights and Rome for 3 nights.

What time of year will you be traveling and what airports are you flying in and out of (assuming you're arriving/departing by air). Are you going anywhere else in Italy or on to another country? All of this makes a difference in creating an optimal plan.

The plan above gives you one full day in Florence and 2 full days in Rome. Unless you've already been to both cities before, this is just barely enough time to scratch their surfaces. I wouldn't plan any trips out of town unless you could add additional days, spend all 5 nights in just one of them, maybe choose Florence for 3-4 nights and the CT for 1-2, or some other options. Again, though, more information would be helpful for making suggestions.

Depending on your arrival and departure times three nights in Rome really only gives you two full days and part of another. That being the case, you might just want to stay the whole time in Rome. But if you do day trip from Rome, consider Ostia Antica just outside Rome. Quick, easy, and inexpensive to get there on public transit. Wonderful ruins and none of the hustle and bustle of Rome.