"Good morning, gentlemen !"
Translation:Bonjour Messieurs !
Even though it uses French words, it is not a widely accepted (or used) French expression: not in France, not in Canada, and not elsewhere in the francophone world. Many consider it an anglicisme because of the construct. There already is a word that means "good morning/good day," and that is bonjour.
If you want to read a tirade about that, here is one from Montreal: Ne me souhaitez pas 'bon matin'
Of course French speakers aren't very consistent about accepting/rejecting anglicismes and thus we have:
Bon week-end in France
Bonne fin de semaine in Quebec
In addition, the spelling of the French "week-end" has recently evolved to accept the alternative "weekend".
From what I understand, "bonne matinée" is acceptable, but only in the particularly early morning.
I could not tell you why exactly, but we only very rarely use "bonne matinée". I don't even remember having ever said it.
Based on the article it sounds like 'Bon matin' is used in Montréal, but it's use is controversial. That said, if, as the comments to the article suggest, France Charbonneau opened meetings of the Charbonneau commission with Bon Matin it seems to be accepted by at least one very respected person.
Messieurs is the plural form of "monsieur". (Monsieurs doesn't exist).
Mesdames et messieurs = ladies and gentlemen
why bother using the word "morning" in the question, if "bonjour" is used any time of day?
Because otherwise learners might not realise that "good morning" is also translated as "bonjour"