To threadstarter: I strongly advise you put a limit on the number of people. 40 people is too many for a sunset shoot? Everyone will be squeezing each other for a space to shoot, not to mention those who are using tripods?
Agree that 40 is a little too much. But from my previous outing experiences, usually full strength is not common, maybe around 70% turnout. However this one may be exceptional. Anyway, splitting group has been suggested by Ringwraith, which is the most feasible way.