Small world typically will go down once they have Haunted Mansion back up after removing its overlay. If memory serves me correctly they’ll have Haunted Mansion go down on a Monday and by the Fri or Sat before the Mon that marks 2 weeks they’ll have it back. They’ll have both Haunted Mansion & Small World up for that weekend & then on Monday have Small world go down for a similar time period. Sat Jan 20th falls right into that weekend where you should see both of them up, so I would plan to have it’s a small world in your first 2 days because likely it will go down by Monday on your 3rd day.
Again, this is based off historical information & as everything with Disneyland subject to change. But either way, I hope this works out for you to be able to enjoy it’s a small world!