Well I'm sure no matter how cold it is, you'll be there
But, just to let you know. FL weather temps are quite fickle in the winter. One day it can be in the 50s and 60s and the next heat up into the 80s or quite the opposite. And sometimes there can be several days of chilliness or quite the opposite, just depends on Mother Nature. December is quite an unpredictble month weatherwise in FL.
Best option for packing, layers...some short sleeves, long sleeves, light jacket, heavy jacket. Long pants or sweats and some shorts. At night you may need the heavier stuff but it really depends...it can be warm at night too.
Now 50s and 60s may feel much warmer to you all then us too

...so it's all relative. Last month one morning it was in the 50s, while dd and I had coats on, there were many people in shorts