Standing rigid like a toy soldier is not really useful, but calling moving "musical expression/audience communication"? I am not sure. I normally "play to the audience" too and may point my bell a little to the left and right, but wandering around - my vote is do what you think is right, but don't make stories up about why.
A lullaby is a pretty intimate thing. I personally would underscore that aspect instead of "spreading it around". There are other tunes that lend themselves better to mass communication.