What is a Christmas fete?

It can be on either or both. I would suggest gathering on Christmas eve with distant relatives just in case of a storm or something you can reschedule to Christmas, or you can have one day for...

well origanally Christmas was celabrated by christians for the celebration of baby Jesus, hen, other people started celebrating it for other reasons

No it was a book about Ebeneser Scrooge and that's what was in the book

Could refer to spherical ornaments on trees ( rarely used by themselves- though I have seen holiday wreaths with balls attached, rather like a ferris wheel, or Balls in the sense of festive dances...

Totally Nothing.