My thoughts were to fly into Venice, stay 2 nights, train to Florence & stay for 3 nights, train to Rome & stay for 4 nights & then train to Sorrento & stay for 3 nights. In Florence take a 1 day guided tour to Cinque Terre. In Sorrento do 1 day to Capri and 1/2 Pompeii but would like to go along Amalfi Coast too. Also would love to take 1 day while in Rome to visit Orvieto. Am I trying to do too much or does it seem reasonable? I want to get hotels booked now but want to make sure this makes sense. Trip is mid October.
Personally, with all those day trips added in I think you're trying to see too much. I don't think you can see the Cinque Terre in one day as a day trip so I wouldn't bother. I would stay 2 nights in Florence (still not enough time) and add that day to your Sorrento time in order to allow you to visit Capri and Pompeii, both full day trips. If it were my trip I would take out the Sorrento part and add days to the other cities you have listed. You can always see Pompeii as a day trip from Rome but this will give you more time to see the Cinque Terre or possibly do an overnight in Orvieto. Donna