Sounds like it's going to be a fabulous trip, ccampeaux! So much to see and do in each of those places. I highly recommend the guided tours.... especially of Pompeii. The tour guides really bring things alive for you, and they have so much knowledge. They can also get you into places much faster by bypassing the long ticket lineups for places such as the Colosseum and the Sistine Chapel.
Learn the money, because some locals will try to stiff you for the change when you purchase things, hoping you won't notice. I had this problem a few times, but they come clean when you challenge them.
Be mindful of your purse and wallet at all times. I've seen purses grabbed from ladies by two people on a Vespa. One drives while the passenger grabs. Be careful in crowds. If there's a lot of jostling it's a distraction to try to get your wallet.
Stay overnight in Capri if you can. The night time ambiance is amazing when all the crowds are gone and the streets are lit with an amazing atmosphere.
If you can, give up a night or two in Rome to travel down the Amalfi coast to Positano or Amalfi. It is much less nerve-wracking to go by boat, but if you don't mind sheer terror you can travel by car or coach. lol
The market in Florence has some amazing deals on men's ties. I saw the exact same ties my husband purchased there for ~ $10 selling for $90 - $150 here in the US. There is also a great bookstore near there which sells awesome cookbooks which I always like to pick up on my travels.
Enjoy enjoy enjoy!
I'll second the Amalfi coast but not by car! I have never had so many times driving a road where I though we were going die, WOW. Having said that, the entire coast from is fabulous and well worth the time to visit no matter what your mode of transportation. The tiny towns with great places to dine right on the road, Positano has wonderful shopping and dining up and down the hill overlooking the sea. We flew into and out of Naples, were not a tall fond of the airport and areas we saw from the Autostrada while driving to/from the coast.
Venice, we stayed twice in the same small hotel near Piazza San Marco......if you'd like name send me a message as it isn't a Marriott property and I don't want to upset some on here! The glass blowing done in Murano is great to visit with small privately owned shops that we found some very beautiful pieces to bring home at better prices. Lido is fun to take an afternoon and wander around, many cafes if I remember correctly.
Congratulations on 35, awesome!