We had a lovely time 16 to 26 December last year (it seems so long ago). There was a really nice atmosphere in the park, people were ‘in the Christmas spirit’, the weather was comfortable (some rain and a little chilly occasionally) so we wore jeans and layers most of the time and the crowds were okay. There were plenty of FPs available, RDs were not too crazy and lots of restaurants had ADR availability. The parks became noticeably busier from 24 December, but even then it was a nice atmosphere. Have fun, whichever dates you choose.