You can edit any holiday to your liking, as well as deleting them or creating new ones. Simply go to the calendar, select the holiday and choose edit. Select the traditions you want. I have edited several holidays in my game as well as added a few new ones. For winterfest I replaced one of the traditions with baking because no Christmas without Christmas cookies for me.
Two things to remember :
- you edit all future holidays of this type. So if you remove santa/father winter he will be gone in all future Christmases. You can always edit the holiday again and change back to the original traditions
- holidays are saved per save file. A change will affect all households in that save. Should you start a new save file, you will have to edit the holidays again if you want a change.