On my bookshelf, I have all sorts of outdated Rick Steves guidebooks from the days my husband I roamed around Europe with our kids. 
In one of his books, he recommended that parents have their kids watch movies to help get them excited about different locations before they arrived. I remember picking up the Italian-dubbed version of Anastasia at the library in Merano where we lived. My Saving the Griffin could be a good choice for kids visiting Tuscany. While most of the book is set at a villa there, several chapters take place in Siena.
Here are a few titles that really brought me back to France and Italy after I returned to the U.S.:
FRANCE
A Cabinet of Earths by Anne Nesbet (Paris)
A Box of Gargoyles by Anne Nesbet (Paris) Previous book’s sequel
Black Radishes by Susan Lynn Meyer (Opens in Paris)
ITALY
The Thief Lord (Venice)
Bloomability by Sharon Creech (Much takes place just north of Italy, but there’s a trip to the Dolomites)
Kristin Wolden Nitz 