Hi Sandra. We've done this twice (from Toronto) and will be doing it again this year.
We have a completely normal Christmas, spend Boxing Day packing like maniacs, and head out early on the 27th. Both times we've had great driving weather with completely clear roads on the way down. The second time we had a light snowfall when we hit Windsor on the way back. Although we always pack winter boots and ski jackets just in case, I'm glad to say we've never needed them. In the car we just wear polar fleece jackets and running shoes.
The book "Along the I-75" by Dave Hunter is a fantastic book! It tells you all the chain gas stations, restaurants and hotels at each exit. In the winter the inner (I-75) route is recommended over the coastal (I-95) route.
The kids actually look forward to the drive down (but not the drive back!).
Cheers,