These ghosts are subjects to the Ghost Queen. They live alongside her in an old forest. Throughout most of their screentime, they're angry about their home being destroyed, but the final line is of one who is being thankful. I imagine these ghosts sounding like young children, because the story describes one of them as small and young, at least for a ghost. So, child-like voices would work perfectly for these roles. Also, I would prefer it if they talk like they're whispering. More than one person can audition because I'm going to need more than one actor.