I find the children's rooms too small. As I have read, you don't have any yet but some are planned. Children nowadays spend much more time in their rooms than before. Currently, we have 10 sqm each in the children's rooms (we are still in our rental apartment). And in my opinion, that is far too little right now. There is a keyboard in one corner, a play crane there, and a dresser, and it already looks cluttered. And when the toys are gone, a bigger bed has to fit in. 15 sqm is just about okay but if you have the chance, make them bigger. Why do you need 20 sqm in the bedroom? You only sleep there, you surely won't spend any other time there.