Florence has no direct flights usually we fly into Amsterdam or Rome and then fly to Florence. You can also fly to Rome and take a train to Florence it is 1.5 hours.
If you are staying at the St Regis or Excelsior they are right across the street, if you stay at the Medici it is an 8 minute walk.
It is formal dress.. not black tie.. but if you want to wear a black tie you are welcome too!