Work colleague of mine was in Lanzarote from dec 26 to Jan 2 and had a great time. Said the flights were very expensive "would have been cheaper to fly to New York". Although not sure you'd want to go to NYC at that time of year, and certainly the Canaries is reasonably priced when you get there. They said Dublin Airport was very quick on the way out, but Lanzarote was chaos on the way back. Lots and lots of English and Irish.
Might be worth thinking of alternatives if flights are really that dear at Christmas, e.g. Mexico, Cuba, North Africa?