mharing,
After self-registration, you can display links to allow the user to:
- Download credentials
- Send credentials to themselves via SMS
- Send Credentials to themselves via email
- Print Credentials.
- Allow the user to download Apple Passbook compatible credentials.
You only have the option to enable the options so that the user can choose. You have the responsibility to build a form to collect all that is necessary for the method displayed. Conceivably the user could choose a method that you do not have any information for.
Honestly, you should choose one solid method and automatically send it to the user via that method, just to keep it simple. The more complicated the workflow, the worse it is for your guests.
This is all in the guest self-registration configuration:

What