Our family of four had a great stay in Florence because we chose Luca's apartment. We were halfway through a tour of Italy and this was a perfect place to experience Florence, rest and recharge. The location is amazing - literally steps from the Duomo. We walked everywhere in 15 minutes or less (Academia, Uffizi, train station, Central Market). The apartment is larger, cleaner and more modern than any we experienced in Italy.
The place was spotless when we arrived and had every amenity a family could need. We took advantage of the kitchen for cooking some meals, did a couple loads of laundry and watched some Netflix on the TV. It is a perfect place for a family like ours with two generous bathrooms, two nice bedrooms and easy access to the sights of the city. You could easily sleep another child on one of the sofas in the living room.
The only negative to consider is that there is some noise in the morning from the street below. The place is very quiet most of the time but can be noisy when the city wakes up and the square down below gets going (~7:00 AM). We were fine with the noise as it lasted less than an hour and is a side-effect of the amazing location.
I recommend Luca's apartment wholeheartedly and will definitely stay there if we are ever lucky enough to visit Florence again.