We are a family with 2 daughters, ages 12 & 16. We'll be in Florence in August and are looking to try some favorites of the locals. We'll be travelling for a couple of weeks and so would like to keep budgets down <100 euro per meal. Thanks!
You need to start by doing a search for Florence on the Italy board. You'll find many suggestions, including a post I did entitled "Florence Report - December 2007" In my post, you will find, among other places, Trattoria Contadino, Vini e Vecchi Sapore, Il Pallotino, Nerbone (in the Mercato Centrale), and Vivi del Chianti (where you eat your panini in the street with lots of other people). Another place for a good lunch is Le Mossacce, near the Duomo. I also suggest you read in my 12/07 post about what you can eat at Teatro del Sale; at lunch, you will eat copious amounts of food, accompanied by free wine, water, coffee, tea, for 100 Euros for the 4 of you. That includes a 5 Euro membership fee for each, but you can go back another time and not pay it again.
I second Vini e Vecchi Sapori, also try Borgo Antico in Santa Spirito. Other places you look at would be Enoteca Fuori Porta on the way to San Minato, Marione near Via Tornabuoni bt possibly not best choice for August! La Posta near the Post Office. Have a super time with your girls.