Bus Question: from Grassina to Florence

Check Rome2rio.com for links to bus schedules, it seems that the last bus from Firenze leaves shortly after 8pm, not time enough for a late dinner. Rome2rio can also give you estimates for taxis.

There is an infrequent interurban bus from Capannuccia to Florence (bus station near SMN railway station), timetables at:
http://www.acvbus.it/orari/354.pdf

Some holes in the timetable may be covered by urban bus #49, going to Grassina; from Grassina urban bus #31 is relatively frequent and goes to San Marco.

As walking to Capannuccia to Grassina is quite long - say, more than half an hour - I guess the best thing to do would be going by car to Grassina and taking the urban bus from there.

From what I've learned, Grassina would be the nearest place for bus transportation.
Q: Is this true?
A: For all intended purposes, yes. The bus is no. 31, operated by ATAF, Florence's municipal bus agency (and my father's employer all his life).
Q: And if so, how frequent are buses?
A: 2 to 3 per hour on average, depending on time of day,
Q: is there a cut off in the evening?
A:Last bus 31 to Grassina departs from Via La Pira (Piazza San Marco area) at 20:43 on weekdays, 20:00 on Saturday, 20:24 on Sunday/holidays.
Q: How much are tickets?
A: €1.20 valid for 90 min from the time of validation at stamping machine (unlimited bus transfers during this timeframe)
or €5.00 valid for one day.
Q: and where can they be purchased?
A: Any tobacconist or shop displaying the ATAF logo.
Q: Is there a shop near the bus stop?
A: If you mean the last stop in Grassina there are many shops. What are you looking for exactly?
Q: Is there a particular ticket I buy for this trip? Round trip? etc?
A: See above.
Q: Where is the drop-off in Florence--or maybe a better question: What is an ideal "central" bus stop that would be near most tourist sites: Duomo, etc. ?
A: Piazza San Marco (last stop).
Q: How early/late do buses run.
A: See above response.
Q: I'm thinking that if we take the bus into Florence in the afternoon and then stay for a late meal, etc. do we need to make sure we know when buses stop running! (Cinderella's dilemma comes to mind!)
A: There is always the taxi if you return late.

Above I gave the Q&A.

But in your shoes, I would drive into Florence. It's not hard. It's a 15 min drive from Grassina. Maybe 20 from Capannuccia.

Drive to Piazza Beccaria and use the underground parking garage there.
There is also another underground parking garage on Via Paolieri, behind the "La Nazione" newspaper headquarters, basically next to Piazza Beccaria.

Use Google Maps for directions. The easiest way is through Via Marco Polo, then along the River Arno (Lungarno Colombo) till you turn right on Viale Amendola. The Beccaria garage is on your left.

From either garage you can walk to the historical center. Both parking lots are open 24/7.