Do I need ExecuteInEditMode() for all scripts?

If I use @script ExecuteInEditMode() for a sort of "master" script that invokes other scripts, do I need to include this statement in these other scripts as well to have it run in edit mode?

No, ExecuteInEditMode just allows the events to work - Awake, Start, Update, etc etc. If your other scripts register with your master script in start, then in that case they will