We went in January with dd(10) and ds(2). It was fabulous! I was pleasantly surprised that ds wasn't afraid of the characters. Especially loved Pluto! It was a wonder, because just 1 month earlier, he wanted nothing to do with Santa. On each of the days we were in port, he slept in a chair on the beach after playing in the water. We did the nursery 3 evenings, so we could see the show without him, but took him to see Disney Dreams, which he loved....so many characters. Also took him to see Island Magic in the afternoon, which is a show geared to the young ones....he enjoyed that too.
As far as the nursery is concerned, he enjoyed it the first 2 nights, and really didn't want to be there the third. We also put him in on the last night of the cruise so I could pack. He's extremely active, and I know he would have unpacked everything before I could get the suitcases zipped.
Just a word of warning.....we loved the cruise so much, we can't wait until we can go without him so we can pamper ourselves with the adult areas and late shows. Harsh? nah! You will love it!