We sailed with a 13 month old in 2016 and a 2.5 year old in 2019. They did offer us a pack and play. I didn’t ask but learned later they may have diaper pails onboard. With the 13 month old, he still was taking a night bottle and I washed them in the sink. It was a great cruise and he loved it, my daughter loved hers at 2.5 also.
there are no diapers allowed in the pools. Pre-COVID the kids club offered toys for checkout, and you could go play with your child in an infant area.