I haven't tried this, but it seems fairly straightforward to me.
Pick the player with the lowest X
Pick the player with the highest X
Pick the player with the lowest Y
Pick the player with the highest Y
scrollTo X=(highestX-lowestX)/2
scrollTo Y=(highestY-lowestY)/2
To determine zoom level, use something like this:
scale = min ( screenWidth/(highestX-lowestX), screenHeight/(highestY-lowestY) )