Why do Americans 'tell' you Good Morning?
Solution 1:
This is my view, incurred upon reading your sentence:
Good Morning is often used (by parents) as the first phrase to say to their children in the morning, more as a regular habit than as a wish.So often, tell is more appropriate decription of their tone. Moreover, parents (like mine) , those who go early to work, often use the phrase to wake their children up from bed, so often the soft tone of wishing won't actually work!
Solution 2:
The author uses the word "tell" because of the wording of the rest of the sentence. If it had been "a good morning" then it would use the word wish, but since the word "a" has been omitted, the word tell makes more sense. Basically, the author uses "good morning" as a quote from the character without using quotation marks: "...to tell her children, 'good morning'" Also, the word 'tell' doesn't always mean you're giving information, sometimes it's simply used as another way of saying "say to." For context, the quote above is essentially equivalent to "...to say to her children 'good morning.'"