CHARITY QUESTION. volunteering in a third world country? PLEASE HELP.?

Hey guys. Next week I am going for an interview to try to get a place to go visit a third world country to see what actually happens over there and to try to help them. I'm only 16 so i think it'd be an amazing experience. By the way please don't say i'm too young as it's our school that does it. I've been fundraising for the past couple of months and i've many other events planned in the upcoming month but for the interview i have to write an essay on why i think i should be able to go and i've a one on one interview then afterwards. I guess what I'm trying to ask is, has anyone any ideas/tips on what to write in the essay and say in the interview? It has to be really good as only 3 people get picked out of our whole cl and i can't describe how badly i want to go and help :( so please any ideas are muchly appreciated <3