Two of my DS's will be in the Oceaneer's club for part of the cruise (the 7 year old doesn't want to go, but we're trying to get him interested). My 4 year old DS LOVED the club last time when he was 3 1/2, and he can't wait to go again. He has never been in day care, so I wasn't sure how he'd handle being away from us, but he had a ball with every event (actually, I just asked him, and he said "it was awesome! we had snack time all the time!"
) Funny he should remember that, but as soon as I just mentioned the club he broke out into a big grin. He also loves the Mickey pool and can't wait to go down the slide for the first time (the CM's said last time he was too small, which he was). If your ds isn't potty trained, he can join my 2 yo in the new kiddie splash area behind the Mickey slide (wasn't there the last time we were on the Wonder 3 years ago).
I will work with my 7 yo, but I think he is reluctant because he missed out on his favorite character last time (goofy). Plus, he's been on three cruises and hasn't had the opportunity to move up to the lab, so being the oldest of the younger group might not be so much fun for him. Well, we'll see.