Itinerary set…now for suggestions for restaurant and not to be missed activities

In Venice, the ciccheti tour. Took it a few years ago with Alessandro (I think! Been a while....) and it was wonderful. I think you just might still find it mentioned in the RS book. Also in Venice we enjoyed the "Secret Itineraries tour" of the Doges Palace. Interesting. We also took a bike tour in Florence with I Bike Italy. It was kind of an uphill climb for the first bit to Fiesole but absolutely worth it for the gorgeous views of Florence. We rode up (and up and up) into the hills a little further and visited a "Renaissance villa winery for olive oil and wine tasting". Really, not THAT tough an uphill....Also some other interesting brief(er) stops. At that time, a wonderful lunch at a taverna was included in the price. Fortunately, it was all downhill back to Florence. We really enjoyed it-lots of fun!

One thing I found fascinating in Venice that Rick mentions only minimally is seeing San Michele, the cemetery island. Be aware that the graves are not shaded, so consider taking an umbrella if it's sunny. Most books that do talk about it focus on the Protestant section where various famous foreigners are buried, but I was even more interested in the other sections. The graves are all different, and many have photos of the person.

Not knowing anything about you, it is a little difficult to make suggestions, but the best thing we did in Venice was batela lessons with ROWVENICE. We were there 4 nights and did not see any of the top museums, believe it or not and still our days were full. (my family requested a museum free time in Venice)
Favorite museum in Rome so far is the Galleria Borghese. The only tour I have done in Rome is the Scavi tour. Very good. I have been to Rome 6-7 times and still have so much to see. Next time I plan on the Villa Doria Pamphilij and a food tour of Testaccio or Vinroma.
It looks like you will only have a day or 2 in each place so I imagine it will be filled with the 2-3 top sites, so maybe not enough time to do much else.
Are you traveling with a tour group and are all your hotels set?

If you give a few more details about yourself, interests, mode of transport, etc you might get more help.
Have fun whatever you decide.

Thank you and yes, it is a whirlwind tour. I have been to Italy once but this will be my husband's first trip. We will be be spending our first night in Bellagio then driving through the recommended passes in the Dolomites. One night in Alta Badia before heading down to Venice for 3 nights. One night in San Marino and then on to Tuscany for 4 nights. Florence = 2 nights and our final 3 nights in Rome. We will return the car prior to getting to Florence.

About us: meandering, enjoying the main sights but I will max out on museums quicker than my husband. Lots of wine and food and hopefully some time to just get lost.

Here's my quick list:
Venice - San Marco, Frari Church, Scuola San Rocco complex, Doge's palace combined with Correr. (Restaurant - Impronta Cafe)
Florence: David, Uffizi, Santa Croce, a tower - you pick (campanile, duomo, palazzo vecchio). I also liked San Miniato - but it's a little off the beaten path.
Rome: St. Peter's Basilica (You can skip museum if you don't like crowds.), pantheon, piazza Navona for fountains (Trevi is under major restoration and largely covered with scaffolding.), colosseum/Roman forum.

For restaurants: you can use RS book and tripadvisor based on your location at the time you are hungry.

Florence - Museo San Marco, Capella Brancacci, Bargello

I would highly recommend grabbing Rick's Italy guidebook as this will have restaurant recommendations as well as highlights of what to see and do. It's essential to have both ahead of time to plan your time and then while you're in Italy to refer to on the spot. I always have ideas about how I want to spend each day before I go but things change and plans are often altered, for various reasons. It's so important to have the book with you to look up sights and restaurants if plans do change. You can purchase Rick's guidebook here: http://travelstore.ricksteves.com/catalog/index.cfm?fuseaction=catalog&parent_id=155

Venice -- after a nice dinner, take a vaporetto on the Grand Canal to see the lights reflected on the water. (We did it after a mediocre dinner, but it was still romantic. )