I've heard the Dream/Fantasy kids clubs are much more crowded than the Magic/Wonder, owing to the larger size of the ship. I haven't been on the older ship so can't compare, but my three year old would not do well in the kids club based on what I saw on the dream. Older kids sprinting around, bowling over little ones, and it is a lot of self-directed free play (they have activities, but kids have to opt in and won't be "shepherded" into the activity by the staff; it is not like clubs at resorts where ever kid is doing the same activity at the same time). Then again, others have young kids who love it. Does your little go to preschool and would be comfortable being left by mom and dad in a crowded place?
Regardless, there is still the nursery, where there is much more one on one attention from the staff and it is very quiet.