Who should be my secondary administrator?

Someone who can act when you cannot, chosen for availability rather than seniority:

• Not your only other director if you travel together - the point is that one event should not remove both.
• Someone who will actually use it - an administrator who has never logged in is a name, not a capability.
• With their own named account - never a shared login, so the audit trail still means something.

Pair this with a break-glass account, so the business is covered even when both people are unavailable.