Allow Planner to Sync to Outlook only for managers direct reports

Syncing holidays with Outlook is really helpful but not for Senior Managers who have a large number of indirect (grandparent) reports. Currently I've been informed that it's impossible to sync only direct reports without indirect ones appearing in Outlook too - that's too much irrelevant information clogging up outlook and making it unwieldy and useless. My CEO really wants to see just the 4 Senior Managers who report to him not the 20 junior team members who might also be off across the company.