newt I believe op's question was more about how to detect the area with the largest number of instances.
— Here is my attempt:
dropbox.com/s/hnhxmtscttgu461/ScrollToBiggestGroup.c3p
If you have exact areas where you know your sprites will be gathering (like those pits in my demo), this can be done much easier. You can put invisible blocks there and simply count the number of sprites overlapping the block, and move the camera to the center of the block with most overlapping sprites.