Disadvantages of bunk beds are that its size for younger children is bestimmet and in just a few years you should replace the furniture. In addition, they are designed for children with little age difference. However, the older child has little desire to sleep on a bunk bed. Before you make such a purchase, it would be good for you to consider whether your children will have a restful sleep if they are to sleep lifted.
However, it is possible that the child is going to sleep on the bottom bed to feel depressed by the limited space. It is not one another to provide the bunk beds, but an angle is also an option. So the children will feel more comfortable. For the higher bunk beds, a closet or a desk can be provided. In this way, it could maximize the space and each child will have their own personal space.