Love this play area over the bed, like the anti-loft bed. I think I& leave off the first couple of steps of the ladder and make it a safer place for the older kids to play with and store their LEGO creations. (Apartment Therapy with loft bed inspiration)
I love the idea of building the bed into the structure of the room for children's rooms. Beds are large pieces of furniture and take up space. This allows for more floor space. I would make the bed into a bunk bed for both Laura and Hannah!
It is ideal to have enough space so each of your child has its own bedroom. But what if you have just one bedroom and four kids? The best way out is opting for bunk beds that will accomodate all of your kids plus will help solving space issues.