Erm... Is it really "funny" as they are reacting to what I read was a horrific accident that landed someone in a hospital?
Was it known to Rita at which event or accident this picture was taken?
IMO if I hadn't heared about the background of this picture from you I would have guessed they (Mosh and kids) are amazed by something (more positive way). And in that light their expressions can come across as funny.