1. Send it from any Correos:
1.1 to Ivar here, in the forum. it is a service he offers and he accepts most anything.
1.2 to the Correos. They hold it for free for 15 days (IIRC) then apply a nominal daily charge.
2. Sent it through the Correos to you reserved lodging in Santiago, but only after you obtain permission from them to do so.
3. Donate surplus to needs gear at an albergue...
Hope this helps.