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Nine points is a quite small number, so I would use some arbitrary boundary instead of trying to build a complex algorithm that might "go wild". I suggest that you use r.grow.distance in grass to create a distance layer around your points, and to set a threshold that would constraint the size of your study area (for instance, the largest distance value ...
While very limited in their presentation, Google Fusion tables have the advantage that they present a very familiar map interface if you have a broad, non-GIS user community. After all, everybody has used Google maps.
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