Charity Ball Event - help!

So my little group want to raise a ton of money to go towards our trip to South Africa in the summer of 2010.

I figured - big money needed means big event required. So a ball seems a good plan. We have no budget but a venue is secured already (my college). It can easily fit 200 in the hall, more if we do a summer one on the field.

Anyone got any words of wisdom on the matter? Some little pieces of advice? (Although big ones are equally well recieved!)