A quick way to decide if the PCs are attacked during camp (when you don’t want to decide yourself) :
Roll a dice (any one; bigger means less probable, smaller more probable) and if the number on it is the number of characters in the party (PC and NPC), there is an attack. Ask for a Take Watch roll, maybe from the PC who was at this place is the watch order (so ask the first one if you roll a 1, the second if you roll a 2, etc.)
Once you’ve determined there is an attack, who to ask for the Watch roll should be determined by what sort of attack is coming. Dusk, dead of night, dawn, that kind of thing.
Maybe when the die comes equal or less than the player characters. More likely with a larger group?
Why wouldn’t you want to decide that? You GM to decide these kinds of things. The usual things I keep in mind when I determine who would need to make the Take Watch roll are “be a fan of the player character” and “show a weakness [of their low WIS]”.
Trickster H yes, I thought it made sense : more people are noticed more easily.
Tim Franzke sometimes, randomness is fun!