If you care to share where you're staying in Reggello, maybe I can map it out and try to figure out why you think it is treacherous to move from there. Unless you're staying at a house on a sharp incline that makes it looks scary to drive up the driveway, Reggello should be a good base as it isn't far from the A1 highway.
In any case, if you're concerned about getting into Florence by car (because you then have to worry about where to park, traffic, not entering the ZTL area, etc), the easiest solution would be to drive down from Reggello to
Figline Valdarno (there is a large parking lot where you can leave your car behind the train station, in Piazza Caduti di Pian d'Albero, then take a passageway under the tracks to get to the station) and from there catch a local train into
Florence's Santa Maria Novella train station.
A great majority of tours use SMN as a meeting point to start off the tour. This way you don't have to worry about driving into Florence. You can check train timetables on
www.trenitalia.com - you do not have to buy train tickets for regional trains ahead of time since they are fixed cost and do not provide seating. You just buy at the train station (some newspaper kiosks and coffee shops will sell tickets by the KM distance, they are similar).