Some years ago we took our daughter to Alaska with us in a pull down top bunk. It worked great and she loved the bunk. The steward lowers it at night and puts it away in the daytime. Honestly, a kid that age does not worry too much about the comfort of the bed. The novelty of the top bunk makes up for it!
You do have to think about organization. It worked well for me to get up and dressed and go sit by the desk while Mom and the kid got ready.
A minisuite is a luxury but I really would spend the money on other things instead! All you really do in the cabin is sleep and shower.
Have a GREAT cruise!