Youmu said:
Why do they have yukata in this size lying around?

It's the will of the universe, plain and simple.

why do they have yukata in this size lying around...

Yukari?

Alice must like visiting.

are these chibis supposed to be as in like puchima@s or as in like touhou puppet play

Because Nazrin stops by...

Simple, in Gensokyou, chibi/mini/dog/inchling characters, or characters temporarily reduced in size due to magic mallet, Yukari fooling around, Moriya Shrine Conspiracy, or Eirin's shady new drug are a common occurrence, and therefore, are things that any good inn must stock up on.

Common sense doesn't exist on Gensokyo

It seems that the inn is within the Shining Needle Castle.