Question: How to modify default admin action "delete\_selected"

Answer: 
<http://docs.djangoproject.com/en/dev/ref/contrib/admin/actions/#adding-actions-to-the-modeladmin>

You can write custom actions, so overwriting the delete\_selected action will allow you to carry out whatever functionality you need (see the warning box on the top of the page which mentions overwriting the delete() action)
DOC:[Disabling actions](https://docs.djangoproject.com/en/1.10/ref/contrib/admin/actions/#disabling-actions)

Disabling a site-wide action

`admin.site.disable_action('delete_selected')`

Otherwise override `ModelAdmin.get_actions`