I think you did a great job with the clothes on the floor. Threats don't work and telling them to do it doesn't work because they will do it on their own time when they are ready if they ever do. If they don't want their stuff to be sent away they will pick them up when they should. Do not let them know they are in the laundry room or when they do it next time they know they will eventually get it back so they will not pick it up.