Do any of your executive admin's authorized to approve expense reports

This idea is a bad one. Authorizing expenses, in theory, is the Approver accepting the responsibility that they validated the expense. If Finance, Accounting or your Auditor questions an expense, do you really feel they should be questioning your Admin? I understand that in some cases an Admin will sign on behalf of their Executive. I do not agree with this approach, but it occurs. But the difference is that the responsibility never leaves the Executive.

Approval without accountability is a useless process.

We allow EAs the ability to approve as proxy for their bosses and allow those managers to set the limits of that proxy (these are not hard coded system limits but rather an understanding between the two parties). We have found it a much more efficient use of the manager's time and allows the EAs to front-run the stories around unusual charges. As head of finance, I reserve the right to circle back with that manager if I need more info to be comfortable with any unusual charge, regardless of who actually approved it. After having the process in place for awhile and creating proper expectations, it is rare for me to question a charge that has not already been vetted by that manager. The EA never wants to be called in to that awkward meeting with an uninformed boss.