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.
A prenominal title is one that a person may legally apply to a professional name in the first person when combined with their warrant, first person titles are often written but most likely presented as abbreviations, they include Adm. for Admiral, Amb. for Ambassador, Col. for Colonel, Dr. for Doctor, Hon. for Honorable, etcetera. A prenominal title may also be a title of respect that may be applied in the third person in reference to a person's standing or status.
Pre-nominal letters refer to other abbreviations like H.E. for His/Her Excellency referring to the current status or standing representative to a high-office of state. Only the highest officer and his/her designated officials, an indigenous chief or an individual designated by a ruling monarch can be referred to as His/Her Excellency.
His/Her Excellency is a formal pronominal title that may be applied in the third person in reference to a person's standing or status at a particular event, place or venue. Goodwill ambassadors generally are not entitled to formal presentation with the pronominal His Excellency or Her Excellency, although among themselves (members of a diplomatic corps) or for public relations those who are actual ambassadors (diplomats) may use it in contextual descriptions.
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.