Venice, Florence, Siena , Cinque Terre

Spend the one night in Venice as you wish then head to Cinque Terre for 2 nights at least.

Stay around Florence 5 nights. The Tuscany/Chianti area Siena etc. are day trips from Florence or choose to stay put in one place in Tuscany and take daytrips.

To me It is no fun packing up stuff and checking in and out of hotels so often.

I would try to spend at least 2 nights in Venice. Your first night you will be jet lagged and might not enjoy it much. I wouldn't want to have to leave the next morning already.
2 nights in Cinque Terre sound good. Rest of the time, stay put in Florence! Do days trips!

You waste so much time changing locations, packing and unpacking, checking in and out of hotels, getting to and waiting at train stations, etc. Not enough time to enjoy where you are.

Suggest narrowing your cities down to two or three.

If you have never been to these places, like Venice, you need at least a couple of day there.

Why not skip the least geographically close location, Cinque Terre. You can always come back. You could take in Pisa and Lucca then.
Siena is a day trip from Florence.

Venice 3 nights
Florence 5 nights
Siena one day from Florence or one night there

So I know it sounds ambitious but we really don't mind changing hotels and are light packers. Here is what we are thinking, Stay in Venice Saturday night and spend the day Saturday and Sunday in Venice and catch the 4 pm train to Cinque Terre. Stay in Cinque Terre Sunday, Monday and Tuesday. Then Siena Wednesday and Thursday with a day trip to Chiani and Spend Friday and Saturday in Florence. We don't fly out until 7pm on Sunday so we should have most of the day Sunday in Florence.

catch the 4 pm train to Cinque Terre

Be certain your lodging is OK with a late arrival. Many places do not have 24x7 presence.

We don't fly out until 7pm on Sunday so we should have most of the day Sunday in Florence.

Be certain to allow plenty of time to get to FCO and look ahead in case of a train strike, which could affect your plans.

Are you intending to drive? It takes 5-6 hours on the train from Venice to one of the towns along the Cinque Terre.

lindy,

You might consider travelling Venice > Florence > Cinque Terre and then back to Florence for your flight. Travel from Venice to the Cinque Terre will take the better part of a day (~6 hours) which uses one day of your already short travel time. Travel times on that route range from about 5H:18M to 7H:01M, depending on which train you choose. If you take the "4 pm" train, you won't arrive until about 10 pm (get used to using 24-hour time when using trains in Italy). If you decide to continue with your present plans, you may want to take an earlier train.

Which of the five towns are you planning to stay in? You'll need to know the specific station names in Italian when buying rail tickets.

As others have mentioned, Siena is easily visited as a day trip from Florence. Travel by Bus is best, as passengers are dropped in the centre of town rather than at the bottom of the hill where the rail station is located.

Have you booked your flight out of Florence yet? Where does the flight go?

To add to Laurel's comment -- Much of Cinque Terre closes down early, arriving at 10PM might not be feasible. I know in Vernazza, everything is closed, except one or 2 bars.