Captain Jill’s Galleon and parts of Splashaway Bay are both perfect for toddlers. The Oasis Lagoon pool has a zero depth entry area with squirting fountains that is fun as well. Babies and toddlers wearing swim diapers are allowed in all of the pools and in the ocean at all the beaches. Here is a link to a map: https://www.royalcaribbean.com/content/dam/royal/resources/pdf/perfect-day-at-cococay-wayfinding-map.pdf
This link gives more tips: https://www.royalcaribbean.com/guides/traveling-with-a-toddler-to-perfect-day-at-cococay#:~:text=CocoCay%20is%20a%20special%20place%20to%20visit.&text=There%20are%20also%20complimentary%20beach,at%20Perfect%20Day%20at%20CocoCay.