You can use server action + hr.holiday workflow for this requirement. It is better than automated action. And i'm not at all confident in automated action for this requirement(leave request,approval...).  

For this you want to create two server action. Setting->Technical->Actions->Server Actions. Create a new server action for leave request to manager Action name:leave_request_manager.

Object:Leave

Action type:Email

Condition:True

Email Address: object.employee_id.parent_id.work_email

Subject: Leave Request from [[ object.employee_id.name ]]

Message: Dear [[object.employee_id.parent_id.name]],

You have one Leave Request from [[ object.employee_id.name ]]. Kindly click the link below to validate the application form. Web: localhost:8069 or ipaddress:8069

Thank you.

Create a new server action for approve mail from manager.

Action name:leave_approval_manager.

Object:Leave

Action type:Email

Condition:True

Email Address: object.employee_id.work_email

Subject: Leave Approval of [[object.employee_id.name]]

Message: Dear [[object.employee_id.name]]

[[object.number_of_days_temp]] day(s) leave from '[[object.date_from]]' to '[[object.date_to]]' has been approved.

Thank You.

Action name:leave_refusal_manager.

Object:Leave

Action type:Email

Condition:True

Email Address: object.employee_id.work_email

Subject: Leave Refusal of [[object.employee_id.name]]

Message: Dear [[object.employee_id.name]]

[[object.number_of_days_temp]] day(s) leave from '[[object.date_from]]' to '[[object.date_to]]' has been refused.

Thank You.

Next step is you want to call these server actions from workflow.

Setting->Technical->Workflow->Workflow->hr.wkf.holidays

confirm->server action->leave_request_manager

validate->server action->leave_approval_manager

refuse->server action->leave_refusal_manager(Kind:Dummy in Workflow)

Thus you can configure it