Why is your director accepting/declining meeting invites from his/her iPhone/iPad? Microsoft's best practices for Exchange recommend only processing invites from desktop clients. Use the iDevices for view only and save yourself a lot of headaches. Better off deactivating new invite pop-ops on the iPhone/iPad entirely, as it is too easy to instinctively click on invites, open Calendar, and make the mistake of accepting invites from the iOS Calendar, which is even a worse practice than accepting from the inbox (which at least deletes the invite and updates calendar).
Either way, processing meetings from iDevices is often the start of calendar desychronization, corrupted calendar data, and lost meetings for heavy Exchange users. We see this all the time with out directors, who (as you know) are exactly the VIPs that cannot afford to miss their meetings.
Check out the following resources put out by Microsoft. Many organizations are also creating internal "best practice" pages below as well:
University of Iowa
University of Michigan