Jane,
I can't help you with a recommendation but I wanted to let you know that we traveled to Tuscany the same week in 2015 and had a great time. The weather was moderate while we were there. There was a little frost a couple of mornings but usually it warmed up to the upper '50's or even mid '60's by the afternoon. We did have one drizzly afternoon, but it coincided with our visit to the Uffizi so it didn't impact our plans. Most days were partly cloudy but there were a couple of days of brilliant sunshine.
Everything was open. We enjoyed visiting some Christmas fairs and seeing the lovely Christmas decorations in Florence, Rome and the smaller towns.
I hope you have a wonderful trip!