I found two other ideas to suport UNICEF via donation of your old money

1) changeforgood-program this for the currencies still circulating and active like the above mentioned - check UNICEF USA Website.
and
2) for all the pre-EURO currencies you might have like Dutch guilders, German mark, Slovenian tolar, Austrian schilling, Portugese escudo, Spanish peseta, Belgian and Luxembourg franc, Maltese Lira, Irish pund, Koruna of Estonia and Slovakia via Euromoney24.com/donations