It's unlikely that I could win any linguistic argument with Q... So,however pedantic it may appear, I think his description vis-a-vis family members is more in the nature of play acting; feigning or posturing, whereas a time-worn Proverb comes to mind that may more accurately decribe your query: A wolf in sheep's' clothing. It has more of the meaning of an intentional camouflage. In Japan the traditional Kabuki theater employs men to perform as the women (called onnagata),, thereby taking on the appearance (and doing it quite convincingly, by the way) of females.
Uncharacteristically, Q side tracked down a rabbit trail on the second part of your question. To shade the conversation,etc., would include descriptive passages from the Diary of Anne Frank, the tragic story of a Jewish child and her family being hidden from the Nazi's during pre-War II by a Dutch family. The parents of the Dutch children living in the same house carefully shaded, i.e., talked-around, with no direct reference to the secret in their attic. To speak openly would have imposed a burden of secrecy on the family members that young children may not have been able to bear. Their are other good descriptions. We do it almost everyday, do we not. We all remember our parents spelling<.I> out words we weren't supposed to know (although that's more of an out and out prevarication in some ways)...