Here is some food for thought--Serve some Formal Language for Meals
Meal times for many families serves as a great opportunity to discuss daily events using formal language. In general, discussions should be encouraged in as many family functions as possible.
As of course, the "earthquake" insurance for this earth shattering linguistic catastrophe (restricted language) is READING to the child every night, almost without fail.
Books are paragons of formal language, and by reading to the child, we come as close as we can to insuring their competence in understanding the complex syntactic and morphological rules of language, not to mention thousands of more words than they would have had.
It may not be an example of good etiquette, but in the Hawking family, they spent much time reading at the diner table. Stephen Hawking, of course, is one of the most brilliant men alive today.