Volunteer Work in Brussels?

Hello I am looking for some information regarding the opportunities to work in Belgium (Brussels).. Preferably on a part-time basis from September to Decemeber. I will be staying in Uccle I am a qualified teacher from South Africa.I have heard about volunteer work, but not sure what this entails. Visa requirements for a work permit will be difficult to get for a short period of time with no definite/guaranteed work. Can anyone help with coaching/english tutoring/anything else in that line of work? Stacey.