Personally, with children of those ages, I would choose a Garden Wing Room at the Contemporary. The rooms are HUGE! There are 2 queen sized beds and a day bed already in the room. The bathroom is also HUGE, and one person can use the toilet and sink, while another is showering and using the double sinks. It is a great layout.
Also, considering your kids' ages, they will LOVE the game room downstairs... the pools are nice, and there is a slide in one of them. MK is also within easy walking distance. There are water craft to rent from the Marina, as well.
I would definitely consider the Contemporary!!!