If the room is small, bunk bed is the best answer to go for in the sibling rooms.
It is also so much fun to sleep in one, whether on top or bottom...
Rocking chairs and swings are fun, right?
How about a bed that swings?
Even when it's very little, since it will be securely fixed to the ceiling; would you find it amusing?
Design is the Salt X Pepper of life. It is not a must, but if you have it, then you have the appetite for life.