It depends on how much junk your kids seem to need!
Ok, over door shoe bag is a big help for all the bathroom stuff. Get the $1 kind at the dollar store and you can throw it away if it is icky... Never used closet organizers...just one more thing to take. After the safety drill, put the lifejackets under the big bed. That frees up a shelf in the closet. The empty suitcases might fit under the bed, or at least stack inside each other.
You will need more hangers--just ask room steward. Do not bother packing these!
The cabins are really well organized to maximize storage space with limited floor space used. Put in perspective, I recently visited my old college dorm with a young lady considering attending school there. I was shocked at how little space we had in the dorms, and found it almost unreal that 2 of us lived in one of those rooms for 3 years. However, at the time, I didn't find it bad.
SO....they will be able to "make do" for a week. It won't be generous, but it will be do-able. Encourage them to not take more than they really need. If you are doing WDW first, do you need everything for the cruise or can some things be shipped home/left in a vehicle? Do they really need 4 hair dryers? There is one in the cabin, but it's not very high powered.
There is a built in chest with drawers (I think one deeper, 2 more shallow). There is a trunk that opens with shelves in it. There is a shelf across the width of the closet (life preservers on this when you enter). There are several shelves in the closet. There is a long hanging space and a short hanging space. There are small shelves in the bathroom. There is a desk with smaller drawers. It's enough, but it's not excessive.
