If you're following the three week itinerary for Italy and love the outdoors ....
If you enjoy hiking/the outdoors and don't really care much about the church/art scene spend more time in the Dolomites and less in Florence. Florence was worth only one day to me just to see David ... that's it (i'm not a church goer-much into the art scene).
Rent a car or utilize the bus service throughout the Dolomites (it's easy to figure out).
Rick's chapter is great about the Dolomites but it skips over several of the smaller villages (such as St. Christina) that have no crowds, no clumsy American tourist/clumsy American tourist attitudes (note I'm an American) . There are SEVERAL ski lifts that take you up into hiking heaven, several huts (some with concessions) and abundance of trails.
The fact that the Dolomites is only "1 star" in the Italy 2016 book is an insult in my opinion for those of us that love the great outdoors.