Wow, Stephen - what an awesome family reunion you've got coming up!
Captain Mickey can't wait to party with you and your family on deck - you guys are in for such a treat. Your little cruisers below 3 years old can have their own party... and they'll get to do it the Disney way! When the big kids go off to enjoy their days and evenings onboard, you can make reservations at It's a Small World Nursery (on the Disney Dream, Fantasy & Magic) or at Flounder's Reef (on the Disney Wonder). Each parent will need to pre-register the little ones, and also arrange specific times on each day that they'll need nursery care. There is an additional cost to this, but it's well worth it - so that everyone can enjoy their vacation.
On embarkation day, each of the Youth Clubs will have an Open House, so that everyone (parents and kids) can come and check out each play area. I highly encourage you to visit the Youth Clubs and speak with the counselors too. Rest assured that your little buccaneers will be well taken cared of while at the clubs... in fact, they may want to stay there for an extended amount of time. Space is limited, so make sure that you plan the hours and make the reservations online as soon as you are able to. As you can imagine, the evening slots are very popular and may fill up quickly.
I hope this helps. Do let us know if we can help in any other way, as you plan for your upcoming family reunion on the high seas!
Have a magical day!
~ Dolly