While I personally can't imagine wanting to, what's wrong with "Goodnight, my prince"?
In Zulu, you would say "Lala ngoxolo" to wish someone goodnight.
In Monaco the official language is French, meaning people would say 'Bonne Nuit' or 'Bonsoir' to say goodnight.
Goodnight, Gracie
Either could be used depending on context. For example, "I said goodnight to Mary" or "I said goodnight and Mary said goodnight, too." The first sentence implies that I directed my words toward Mary and not toward someone else. The second sentence means that both Mary and I said goodnight, without specifying to whom we addressed our words. You would generally say goodnight to someone. You would rarely use the word "too" after goodnight. If you did, it would mean "also."
Almost all of New Zealand speaks English. So 'Goodnight' would be 'Goodnight.'
You can say "lafi" to say goodnight in Mandinka.
In Berber, you can say "tanemirt" to say goodnight.
You would say, "Good night,I love you".
"Goodnight".
goodnight
goodnight!
In Fulani, you can say "Jaama wolof" to say goodnight.