Dear tuscan experts, I am flying in to Florence, touching down 8 am, and have 2 days for the above mentioned cities. Please let me know if the following plan will work 
Day 1: Pick up car from florence airport, drive down Chiantigiana road and stop at Greve in Chianti and then Panzano.
Now the question is, shall we continue to San Gimignano and then overnight there or Siena? Then spend the 2nd day in Siena before returning to Florence in the evening?
Day 2: Siena and potentially Val d'orcia before driving back to FLorence airport to return the car and take a train to florence for the remaining trip?
Really appreciate some advice on these. Thanks

Day 1: Pick up car from florence airport, drive down Chiantigiana road and stop at Greve in Chianti and then Panzano.
Now the question is, shall we continue to San Gimignano and then overnight there or Siena? Then spend the 2nd day in Siena before returning to Florence in the evening?
Day 2: Siena and potentially Val d'orcia before driving back to FLorence airport to return the car and take a train to florence for the remaining trip?
Really appreciate some advice on these. Thanks