Hello, I have three children who each have a pretty small bedroom each (all the exact same dimensions)
I've attached a photo of my middle son's bedroom (he is 6) and this layout works fairly well. He has a lot of storage in the wardrobe for his clothes, coats, bedding and toys, and one side also has a desk in there he can sit at, but it is a massive wardrobe for a small room. He has a single bed.
My elder son has a small double and I can't figure out how best to make use of the space. If I can get it to work well, I would also get my youngest a small double when she moves out of her toddler bed as it's so much nicer for laying with them for bedtime chats, stories etc and for as they get bigger. If not she will just have a single and the same layout as in the photo I guess.
The bedrooms are 2.7m x 2.3m with pocket doors. They have a big window each which limits storage options a bit!