April in Tuscany
Dear rapz,
April is a nice month to visit Tuscany. The weather is mild and generally sunny. The countryside is in bloom and is colored with different nuances of pink, orange, white and green.
In April there are events. At the moment it's hard to find more information about festivals since there is no official calendar. We try to update our own 
events calender as we learn of events going on. But there is a nice 
antiques market on the fourth weekend of every month in 
Montevarchi, close to your accommodation, as well as in 
Castiglion Fiorentino.
I think moving by 
train to reach 
Florence, 
Pisa and 
Lucca is the best choice. Parking in big cities is always difficult and expensive. You'll save money and headaches by using the train 
 
As for 
Siena, I suggest you take the 
bus SITA SI91 from Montevarchi to Siena directly. It's faster than the train.
Since you'll be staying in Terranuova Bracciolini I also recommend you visit 
Arezzo which is not far. It's the birth place of many famous artists, such as 
Giorgio Vasari and Pietro Aretino. Inside the 
Basilica of St Francis you can admire the masterpiece of Renaissance artist 
Piero della Francesca, a fresco cycle depicting the 
History of the True Cross. A quick note: the movie 
Life is Beautiful (La Vita è Bella) by Roberto Benigni was shot in Arezzo so if you've seen it you'll recognize some of the squares.
You can also visit the beautiful Etruscan city of 
Cortona. The center is nice and has beautiful Renaissance churches and buildings, where you find good restaurants and shops.
Certainly the 
Chianti region deserves a visit. It's world renowned for its beauty and wine. The landscape is designed by its vineyards and olive groves. There are many wineries, farms and restaurants where you can have good food and taste Chianti wine. See our article "
Discovering Chianti" to find more information on what to see in Chianti.
Regarding 
Cinque Terre, I think it can be a "tour de force". Driving from Florence to Cinque Terre takes 
no less than 2 hours and half. Then the time for visiting the area, eating and then back. It can be hard. I also have to say that the highway to Cinque Terre is not a nice one. It's pretty narrow (as highway) and windy.
I also suggest you visit the southern area of Siena called the 
Val D'Orcia. As Chianti, it's famous for its wine and landscape. The most beautiful towns are 
Montepulciano, 
Montalcino and 
Pienza. All towns are picturesque and have good wineries.
I hope it helps. Don't hesitate to come back and ask more questions if you have any!