Yeah, Secret Santa kind of works with more or less people as you get as many works as you have receivers
(provided everyone sticks to their commitment). If we are running low on participants, I feel like the Advent Calendar may be harder as there are (at least...) 24 works to go.
On the other hand, the Advent Calendar would perhaps be easiest to supply with some Golden Oldies, as Christmas / Yule -related works are the focus every year. Also the oldest Advent Calendars are a lot older than the oldest Chapter Break Fillers.
So, what I'm getting at, would probably be the following suggestion:
- run YoinkTober
- when chapter break timing is known, find out whether the drive is there to go through with it "properly", if not, choose a substitute (substitutes include: combine into YoinkTober; reruns; improvized small works; other, please specify)
- run Secret Santa
- run Advent Calendar with the understanding that works from previous years will be used to supplement new works, to avoid putting pressure on anyone to promise more works than they feel comfortable with
If announcing any of these events it becomes evident that there won't be enough creators, it can be canceled or done as a partial (with the exception of SS, but that, as already mentioned, sort of resizes itself).