You can't speak freely at home when your little children hear you, because there is a risk they will repeat your words in public, which can get you in trouble. It's probably also quite dangerous with teenagers around; they may get a wrong idea about appearing cool to their peers by saying something that can't be say, and then get reported on.

First, you need to make sure your children understand the magnitude of danger from repeating what they heard at home. That requires some maturity and intelligence, but more importantly the idea that "there are important truths that you can get punished for saying in a wrong place" is itself one of those important truths that you can get punished for saying in a wrong place, so you either need to approach this very very carefully or take a risk and hope for the best.