Age appropriate

At the moment I am working through the design process with two girls. Twins. Who are nine years old. We are working on a new design for their bedrooms, and discovering as we go along that they are kind of stuck. Not quite a child, but not quite a teenager either. Playing with dolls still features heavily on their agenda, but the word 'babyish' now features in their vocabulary. 

Quite the conundrum! 

I love these works by blancucha. But perhaps they are too young? Or too old?

What do you think? Any tips??