I tend to handle the two different types of situations differently. Is this an action that is governed by privilege and by state of the object.
If the person does not have enough privileges to do an action, I hide the option, they do not know they can perform the action.
If the option is not available because the object is not in a state that can use that option, I disable it, allowing the option to be visible to the user, but no action can be done.
From your examples:
I would not have "Create Master Event" as an option. The user has insufficient privileges to view it.
I would have the Delete button visible to the administrators. Then depending on how you do the rest of the site (a lot of visible text, tooltips, help icon, etc) I would follow that convention about informing the user why the button is not usable at this time. And possibly putting a timer on, above, near the button with either how old the post is or how long until it can be deleted.
