You could consider wind surfing on Lake Garda if you have a couple days to spare.

Cremona is not a tourist hot spot but an interesting little town if your path heads that way. A restaurant called Osteria Pane e Salame has amazing risotto.

You'll probably want to spend the bulk of your time exploring Tuscany on the way to Rome. My top two recommendations in Florence are the David and climbing the Duomo but there are so many things to see there. The fruit flavored gelato at Festival del Gelato is life changing, especially peach.

Siena is a cool town between Florence and Rome. Best restaurant in Siena is La Taverna di San Giuseppe which requires reservations well in advance. Just hanging out in the main piazza is fun and relaxing.

If you're driving you might consider staying at an agriturismo at some point. They come in many shapes and sizes but I'd look for one with updated rooms and a nice restaurant or meals prepared from local ingredients. They're generally tucked away off the beaten path and make a nice getaway after crowded cities.

For most of the major sites you'll need to buy timed entry tickets online, especially in Florence and Rome. Check available dates to see how far in advance they sell tickets and jump on them as soon as you know your dates in each location.

Many opinions on gelato in Rome but della Palma is pure quality. The Trastevere neighborhood has lots of good restaurants and my favorite is kind of a hole in the wall called Alle Fratte di Trastevere where a Napoletana grandma runs the kitchen.

Outside Rome there's a fascinating sculpture garden at Bomarzo that is one the best things I've seen. Kind of hard to get there without a car though.

Some nice beaches outside Rome too which are worth looking up if you're into that kind of vacation.