While there are differences between Candid and Photojournalistic photography, the contrast is not that vast. In fact, there are more similarities than differences, in my opinion. When contemplating a photojournalistic approach, think Story-telling.
The photo itself should be enough to make a reasonable assumption of what is happening. It may not determine time, places or names, but it will express the type of event or action that is taking place at that moment.
A candid photo doesn't necasserily have to explain itself. Where photojournalism is more useful for an event, candid photography can be applied in everyday life.
In each case, the subjects are generally unaware of your presence. They may be aware that a photographer is present, (i.e. in the same room) but they will not know you are photographing them at that particular moment.
The bottom line is, photojournalism conveys a story (purists would say a news story, but I would argue that point).
Candid photography conveys more of a feeling. Can a photograph be both? Yes! However, anyone can take a candid photo. A trained photojournalist knows how to tell a good story.
Remember, when opportunities arise, take your best shot.