Oh Lucinda, you will have a wonderful trip!
You can easily fill two days in Rome with the big stuff. I've been all around the world, but still found ancient Rome to be the most awe-inspiring. For me it was the Forum that was most amazing.
We stayed in a hotel near the Pantheon. Just around the corner is the church where Galileo was excommunicated. It's called Santa Maria sopra Minerva. You can get a great gelato across from the Pantheon (when looking out to the square from the entrance to the Pantheon, the gelato place is in the far right corner, or close to it).
We also enjoyed a quiet walk through the Jewish ghetto.
I haven't been to Florence
I went to a conference in Bologna back in 1990. What I remember most about that city is the unfinished Duomo, Santa Stefano (a religious complex), and the unbelievably good food (also featured in all it's mouth-watering beauty in shop windows). This is a region where you should eat Parmigiano-Reggiano cheese and prosciutto di Parma ham. And little almond candies (like marzipan) and cakes and cookies and...
From Bologna I took a day trip to Ravenna, known for its churches with amazing mosaics. I also remember a wonderful "green sauce" served in this area with meat and fish. It's made from parsley, giardinera (pickled vegetables), oil and
Milan is a busy, cosmopolitan city with very expensive clothes. My Italian friends tell me that many Italian business women in northern Italy own only 1 or 2 suits that they wear everyday with a new blouse - but they save up to buy the best designer they can afford.
We have friends who live north of the city in Busto Arsenio. They take us driving in the hills north of Milan to a place called Sacro Monte di Varese
http://www.sacromonte.it/info_sacromonte.html. It's a UNESCO World Heritage site. Good for hiking around and lots of little places to have lunch.
Haven't been to Portofino... but I have been to Genoa (Genova to the Italians). Eat seafood, gnocchi and pesto!
Naples... haven't been there either. Probably the best place on the trip to plan to try aranciata (fried cheesy rice balls filled with tomato and meat sauce) based on what my Italian friends grandmas made for holidays - they were all from Naples or Sicily.
Verona - Romeo, Romeo, were for art thou Romeo? While Romeo and Juliet are fictional characters, you can still visit a balcony said to be Juliet's. I think the arena is the highlight in Verona. If you are drinking wine, this would be a place to try Prosecco (Italian sparkling wine) and risotto, which is big in the rice growing region of Italy .
Venice - we went to Venice on a very hot summer day and it was packed. Try to have coffee at Caffe Florian on St. Mark's Square - very famous!
http://www.caffeflorian.com/ I love going to the outdoor markets in any town. I love food (can you tell) and a market is a great place to buy great cheeses, bread, ham, olives, fruit and nuts. All the attractions will start to look the same after awhile. But it doesn't matter because you can have a great time in Italy just sitting in a square eating and drinking and watching people. Have coffee or an italian soda or a campari and just soak it in.
HAVE FUN!!!!! (and have a Margherita pizza for Twirl!)