One rider should (last one in group) wait (safely) at any turns for anyone seperated from the group and so on until all are together again, having the lead rider(road captain) stop then take over the group again can be done but a lot safer using the last man method,
If a large group split into small groups no more than six, a lot easier to control and safer, the idea of a million Rockets riding down the road reminds me of the Simpson episode with the Harley riders look at me--look at me -vroom vroom.
Nothing worse then having 20-30 eiders pull into a gas station then about 30-45min later they finally leave far too much riding time lost.
If riding in a large or for that matter any group the most important thing to do is have a safety meeting with all riders present before taking off.