Generalized and Specific Titles
There are many titles that can be added to personal names which can serve generically when combined to describe an organization's name; "Goodwill Ambassador" and its inverse "Ambassador of Goodwill" is a single title that can be presented or utilized in a generic sense when presented inside of a realm, country, dominion or territory relative to it, but needs to be attributed and specified when presented outside of a territory or in the whole world, such as on the Internet. A title should also be an active title when presented in order to be exercised, recognized and utilized. Improper or non-specific designations should not and generally are not fully recognized, if they are not presented under protocol.
Goodwill Ambassador as a Proper Title
There are several different ways the term "goodwill ambassador" can be used as a title, but most importantly is that it is capitalized using title case if as a title, it refers to someone who is figuratively in occupation or role written in lower case, when talking about several it would be "goodwill ambassadors".
Mr/Miss/Mrs/Dr/Hon Firstname Middlename Lastname, [ORG ID] Goodwill Ambassador
Mr/Miss/Mrs/Dr/Hon Firstname Middlename Lastname, [ORG ID] Goodwill Ambassador to [COUNTRY]
Mr/Miss/Mrs/Dr/Hon Firstname Middlename Lastname, [ORG ID] Goodwill Ambassador of [MISSION]
Mr/Miss/Mrs/Dr/Hon Firstname Middlename Lastname, Goodwill Ambassador of [Place Name]
A goodwill ambassador would never want to improperly present themselves or they may be considered a fake or someone with ingenuine credentials, all goodwill ambassadors are briefed on how they may or may not use their titles and affiliation on assignment.