Regarding the Christmas Stream (Dec.20th), it seems Gloomwood is getting a new area/update mid-December. They say it'll be available during the Steam Winter Sale, and that's should be around Dec.18th. If I remember correctly, Gloomwood also has seasonal environmental changes (jack o'lanterns during October, snow and festive decorations in December) so it'd be season-appropriate.
They don't do save compatibility with version changes, though, so I could either play with an old version save and hope it doesn't bug out, or I'd have 48 hours to grind through the game from the start and catch up to the new content in time for Saturday. May I'll get lucky and it'll release before the 18th, but we'll see.
In the event Gloomwood doesn't work out, I'm planning to dredge up Shadows of Doubt as a backup plan, since I had an idea on how to twist that into Yuletide content, after a fashion. I was almost going to consider trying Brume, the sequel to Kona (another previous Christmas Stream game) but the amount they charge for it seems a little egregious if it's at all like what I remember from the first game, so I passed on it.
Anyway, Gloomwood or Shadows of Doubt it'll be. Either way, Christmas is saved.