We had a wonderful stay at the Renaissance Palace in Santa Croce. We travelled as a family of 8, with family members 1-81 years old, and the accommodation was excellent for all of us. Very spacious and well equipped main area/living room/open kitchen. Private bedrooms with lots of space and comfort. (As others have written: would only not recommend for seniors with physical impairments as the stairs without handrails might be uncomfortable.)
There are for sure countless generic accommodation options in Florence, but here you will stay at the classic but modernized family home (with all of its quirks) of a real Florentine family, with spiral staircases and views into a private Renaissance garden. The flair of the location, just a few steps off Santa Croce Square, cannot be beaten!