You have plenty of time to ruminate on this one - so don't rush in. Take your time, try plenty of things on, and find the perfect ensemble. I always find that December weddings tend to feel very romantic, a little bit fairy-tale. For this reason, velvets, fur trims, satins and gold/claret colours tend to work well. Since you are Mother of the Bride, do check what the groom's mother will be wearing - it matters that you don't clash!