The great getaway of the second half of December is only matched by late July for volume, as everyone heads off for some sun for Christmas and New Year, or else a ski break. As November, there is nowhere warm within four hours flying time - resorts like Tenerife get one or two wet days a week and can barely manage 15 degrees. The Red Sea resorts can be windy, and too chilly even for sunbathing. Even that reliable standby Dubai is barely hot, in the mid 20s, and likely to be overcast alot of the time.
The main holiday activities in Europe in December are skiing - after the 15th - and shopping. Non-ski holidays reviolve around Christmas markets and city breaks - consider Munich, Salzburg, Bruges and Cologne. But wrap up!
The main question on long haul holidays in December is - are you prepared to pay the rates? If not you will need to go and return in time for Christmas, otherwise prices will be at their peak, and the more you want sun, the further you will have to go, because the further you go south, the better the chance of heat. Best destinations in December are South Africa, Australia and Argentina, while in the mid band, unless you are interested in an adventure in Mali - and why not? - you should consider Mexico, where the summer rains are long gone, the Madlives, or northern India. Further east, in Thailand, Malaysia and Bali, it's most likely raining. Good luck!
Take a flight directly after you've polished off the turkey for Christmas lunch, that evening, and fly to Mombasa and rent a beach house in Watamu. Don't come back for three weeks. Eat locally caught fish and do nothing, and come back totally relaxed and, more to the point, still solvent...