You may not need to use flash if the ambient lighting is sufficient. Natural light is better than uneven strobe-lighting. Using SB-800 at near distance will definitely result in light fall-off, unless you keep a considerable distance from the subjects. Quoting the 'inverse square law' of light fall-off:
"the light falling on any object will be inversely proportional to the square of its distance from the light source"In other words, the further the light source is from the subject, the greater depth of coverage achieved. This is at the expense of the strobe firing at full capacity, and assuming your strobe is powerful enough to light up the subjects correctly from a distance.