Hey John,
Thanks for getting in touch with us!
You are right about the template tickets/email.php, this is the one used to send the tickets out. Now regarding the extra information you want to add, that can be stored in custom fields or maybe in the page excerpt. Once that’s added you’ll need to create a template override of the tickets/email.php file and add the custom code needed to pull this information from the page (more info on how to do this in our themer’s guide).
Another option is to hook to the tribe_tickets_ticket_email_ticket_bottom action. I guess it depends on where you need to place this information.
Please let me know if this helps,
Best,
Nico