The choices are:
Jack: because as always the whole mess is his fault.
John Hart: oh him as Santa is too good to pass up.
Rhys: he is jolly enough to be the best Santa
Owen: Owen been jolly enough said.
The only one who can't dress up as Santa is Ianto, I know who wouldn't want Santa Ianto coming to their house?
An input would be welcomed, I have half the story written, I just got stuck at who should play Santa and it plays an important role in the story and I just can't decide between these four.