Job Execution over group of host once for all

Im making a complex template for patching my linux hosts. Im going to make a template (task) wich render another templates (subtasks) who execute patching subtasks (downtime nagios, snapshot, yum, reboot…) All this task will be run for each time and thats ok obviusly. But i have one task, send email, that i want to be run once for all host, not one time for each host. I want to send one email to notify begining of patching tasks o and another for the end.
If i patch 50 hosts i dont want to send 50 begining mails and 50 ending mails, only one begining and one for end.

Is it posible?? How? Im thinking in hooks, but i suppose it apply to all remote execution templatesand cant be only for one template.

Thanks in avance!!!