Here is my tentative itinerary:

Day 1 – Wed - Arrive at Venice Airport 9am, explore on our own, Gondola ride at night
Day 2 – Thurs - Walking tour of Venice, depart for Florence around 6:30
Day 3 – Fri - Florence - Statue of David & Duomo
Day 4 – Sat - Florence – Uffizi Gallery
Day 5 - Sun - Sienna/Cortona or Bologna
Day 6 - Mon - Sienna/Cortona or Bologna
Day 7 - Tues - Rome - Arrive early morning, visit the Vatican
Day 8 - Wed - Rome - Walking tour
Day 9 - Thurs - Rome - Ancient Rome tour
Day 10 - Fri - Sorrento (Visit Pompei or Herculaneum on the way)
Day 11 - Sat - Sorrento - Day trip to Capri
Day 12 - Sun - Sorrento
Day 13 - Mon - Fly home from Naples or Rome

I know that this is a lot to do, is it reasonable? Also, what is your opinion on Tuscany (either Siena or Cortona) vs. Emilia Romagna (Bologna)? Any other changes you would suggest? Thanks for your help.

I would highly suggest Tuscany. I'd try for a smaller town than Siena to break up the environs a bit...apparently you are doing this using trains for transport? Consider taking a bus into Chianti country from Florence, and then on to Siena to catch a train to Rome.

Yes, this is a packed itinerary. You don't seem to allow for jetlag or sleepiness after an all night flight. (I assume the all night flight from your arrival time in Venice.)

Bologna is between Venice and Florence on the train line. So if you were going to do it, it should come before Florence.

But I'd take those 2 days, give one to Venice and one to Sorrento, so you could spend a day on the Amalfi coast -- by bus or boat. You're so close, it would be a shame not to see something of it. On your extra day in Venice you could take the vaporetto to the nearby islands of Burano and Murano. Or Torcello or the Lido.

Save the Tuscan countryside for when you have more time and/or a car.

Would it make more sense to stay in the Amalfi coast? This is really where I wanted to go, but every travel agent seems to have us staying in Sorrento as a base. We are not using a travel agent to book anything though.

I've thought about the jet lag, I figure we can take a nap a bit later in the afternoon before dinner. It's not ideal, but I've done it before in Europe.

Wow. 13 days and only 1 in Venice? And your very first day off the plane at that? That would definitely not be my choice. I would shave a day or two off other destinations (or even cut one out completely) to allow at least 3 days in Venice at the start of your trip.

Go for it. May you still be awake for that evening gondola ride!

Sorrento is more convenient for inland travel than most of the Amalfi Coast towns. Boat travel easier.

If you are like the rest of us, you'll go back!

I could never stay awake when jet lag hit-am jealous.

You only have 12 days---pick 4 destinations and enjoy them. Give Venice 3 nites at least. I would end in Rome.

I guess I should mention that there are 5 people going, 2 who are arriving on day 4. One person wants to do all the touristy things, 2 want a very relaxed vacation and the other 2 want something in between. So the order of things is a bit limited because the two arriving later don't really have much interest in Venice or Florence. I'm also the only one who is willing to do much planning.

All of the places you list are wonderful and well worth visiting. As are many other places in Italy: Ravenna's mosaics are absolutely sumptuous. Perugia is a jewel. Assisi can be charming.

So here is the problem: when you keep going from place to place to place, it can start to become a blur. You're having a wonderful time, but when you get back home, was that little restaurant with the terrific linguine and amazing local wine in Bologna or in Sorrento? And where did the ceramic dish come from?

I think you'll enjoy yourselves if you take the trip that you outlined. And I think you'll enjoy yourselves even more if you spend more time in Venice, spend much more time in Tuscany, and save Sorrento/Naples for another trip.

Don

Being put in the role of professional trip planner for a group of 5 people, arriving at different times, with completely different expectations/desires from the trip, with no one else wanting to help... is a HUGE undertaking!

He who does the work gets to call the shots.
Plan a good trip and let them adapt--or stay home.

They seem to be pretty willing to compromise and I've done enough traveling that I'm ok planning it once we decide on the itinerary. It seems overwhelming, but if I just take it piece by piece, it's fine. We had looked into travel agents, but the packages they come back with just seem so expensive and they aren't doing anything special or different.

When is this trip?

Your proposed itinerary involves too much moving around for me, but that's me. I will say that moving as a group of five may be slower than you think, especially since there seems to be the entire range of goals/desires ("touristy," "relaxed, "in between"). I hope there is agreement on how early, structured, fast, expensive, etc., each day will be.

Ditto DonTopaz' suggestions.

We did a longer version of this itinerary last spring (spent 4 nights each in Venice, Florence and Rome plus 3 in Cortona, 2 in Siena and 2 in Sorrento- and loved having that much time)- but I'd shorten Florence over either Venice or Rome. Loved Cortona and other Tuscan villages like Montepulciano, San Gimignano, Monteriggioni but weren't too smitten with Siena. Loved Sorrento and used it as a base by train for Pompeii, but we spent most of a day at Pompeii... I'd probably give myself 1 more day in Venice than you've allotted, cut Florence by a day or possibly cut Sorrento by a day (Just enjoy Pompeii and Sorrento and save the rest of the Amalfi coast for another trip).
One question: how are you moving from place to place? A car is useful for Tuscany but a hassle in the cities...We took a bus from Rome to Sorrento to avoid the Naples train station w/luggage and the hassles we'd heard about re: Naples in general- and the bus was an easy 3 1/2 hrs or so direct. We picked up a car leaving Sorrento to drive north to Tuscany, but trained between Florence and Venice (we began in Rome and ended in Venice, so just the reverse of your plan).
Keep in mind the travel times involved in getting from place to place, as they will eat up more time than you might imagine. After that- plan as best you can and then enjoy! At least you're not staying just 1 night in each of the places you've outlined!

Ok, so I think we have modified this a bit. We will do two nights in Venice, but leave early in the morning on day three for Florence. We will spend the next 4 nights in Florence with a day trip to Siena or Cortona and maybe one to Bologna as well. This way we are not moving around quite as much and we can adjust what we want to do in Florence as we are there. I think the rest will remain the same after that, again tours are not set in stone at this point, it was just a general idea of what we wanted to do.