Thanks for the info, will check out the places you mention. Will need much more than a container as there is furniture too.
I am not aware if there is any organization that will pick up such items as old clothes, but there used to be places where you could dump them. One such big container was present at Villaggio near gate # 4. I saw another one just outside Qatar Charity office on Muaither Street commonly known as Sharah e Tejari. You could put your package in them.