Have a blast! If you would like to hear more about this cruise, check out episode 194 of the Vacationeers Theme Parks and More podcast. Spotify link is here or it can be found wherever you stream your podcasts. open.spotify.com/episode/1nnjNzwxYLBpHMZpCgvkXs?si=58ae9d6b68004ff3
There's plenty to do on the ship for them and at those ages they should be able to hang out in the same kids zones. Also, I have found that if one might be a little too young for an area they are willing to make exceptions so siblings to hang out together. Everyone will have a blast, so enjoy it!