Heather, I think you could also apply permissions to Enable/disable this button from the Ribbon customization tool. And that way you could specify that it should show only for the Admins.
Prior to using the Ribbon Workbench, the security for the Opportunity needs to be checked. In this example, the "Delete" option for the Opportunity entity needs to be set to "None" for the security role.
Create a solution file that contains only the Opportunity entity.
Open Ribbon Workbench and pick the solution just created.
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