Generally event shooting in Singapore are mostly indoors and the lighting conditions are generally not that good.
D5000 is not known for good ISO performance and hence external flash is almost a must for shooting indoors. Even if you have D3s, generally people will still have external flash.
My recommendation is rent/get an external flash like SB600/700 and try it out but since you are not the main pg on that day, take note to not get in their way and don't use your flash without checking as it might affect their metering during critical moments. What I mean is when they are taking, your flash happens to fire at the same time and their images might be over-exposed. For some moments, there might not be a chance for them to re-take. So be mindful of that.