I think it would be cool to have some event related missions for bigger events like halloween or christmas, just added to the daily pool while the event is ongoing, and probably only during the whole days of the event (so not on the 1st and last day of the event where it starts/ends at 12).
They could also have event related prizes, like candy instead of coke/alcohol for halloween and one of the presents for christmas.

For halloween it could be something like:
Visit x amount of houses
explore x haunted houses

For christmas it could be:

Find x amount of presents