It just checked the schedule for the entire year and there are two days where they have 4 ships scheduled. I have never been there, but logistically, how can they do this?
Here is a list of 3 and 4 calling ships at Coco Cay as of 1/17/20 as provided by https://www.cruisetimetables.com/cruises-to-coco-cay-bahamas.html
27 January 2020
24 February 2020
02 April 2020
09 April 2020
16 April 2020
30 April 2020
20 May 2020
27 May 2020
03 June 2020
17 June 2020
30 June 2020 - Four ship.
07 July 2020 - Four ship.
14 July 2020
28 July 2020
09 September 2020
07 October 2020