Hi Sarah,
Photographing a public event is never easy, particularly if it is an ANZAC dawn ceremony.
One of the big challenges facing a photographer are the boundaries placed about such events. Some of these boundaries are physical, like the fence that is obvious in the far side of this picture. That being said, one of the stronger boundaries is our own fear of getting close to people.
Because of these boundaries we usually do not get close enough to a subject when making a photo.
The great Magnum photographer, Robert Capa once said, "If your pictures aren't good enough, you're not close enough", and this is the problem with this photograph. The photo was made some distance away from the subject and as a result there is no real sense of purpose to what you are trying to do here.
One of the simplest ways to improve this photograph would have been to have changed the wide-angle lens for a telephoto lens. In doing this you could zoom in on this elderly soldier and make more of a story. We would be able to see more of his face and understand his emotions on the day.
There is just one challenge in switching to a telephoto lens on a flat and overcast day like this and that is the challenges you face with exposure. As you increase your focal length (in other words change from a wide to a telephoto lens) you also need to make sure that your shutter speed is fast enough to avoid blurring the photograph through camera movement. If your lens has built-in image-stabilisation then make sure it is turned on, but alternatively it is not a bad idea to use a tripod on a gloomy day like this.
Alternatively, immediately after the service quietly go up to this gentleman and ask if you can make as portrait; chances are he will let you, and you will get a stronger photograph if you get close enough.
Cheers,
Anthony.