I have not cruised with a 3-yr old, but we went last time on a 4-nighter with a recently-turned 4 yr. old. She was a little leary of the kids' club at first, but her mom stayed and played with her there on the first day when you sign in, and she wanted to go back. The good news is that they give you a beeper, so even if you drop him off and he changes his mind after 20 minutes, they will page you to come check on him. They have so much to do there, and the CM's are great.
Besides the kids club, the Mickey pool can be crowded, but it would be a fun time for your little guy, especially if you can go at not peak times. He will have non-threatening character interactions in the kids club, as well as character meets on other spots on the ship. It is such a wonderful family environment ... if I were you, I wouldn't miss it for anything!
Be aware: I know someone who couldn't get the main (6:00 seating) on the 4 night anytime this fall (from August through December) for her family of 6... all the main seatings were already taken. If you are thinking about this year... HURRY! If you are considering next year, HURRY! The prices are still "early bird specials" for 2005, except at Spring break. DU is offering a special right now. Check out their offer. That's who we are using, and we are very pleased.
Good luck... go for it!
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