You can buy all/most of those things in Negril, and support local businesses as well as the kids. There is a stationery/supplies shop next to ValueMaster and places all over with hair beads etc. and shoe polish at the grocery store or sometimes from a vendor on the street. Only thing that might not be easy to get to and purchase during your vacation time is black socks and backpacks.

If you give the organization a money donation, they can purchase in bulk, and stretch it even further. I don't know if they get a waiver on GCT but if they do, the purchasing power of your donation increases 16.5%.