last year, my 8-year old son (during a planet exhibition) said, "that freaked my heart." (something he picked up from my friend's daughter who was sitting next to him.) and i asked him, "what does that mean, Jonathan?" and he said, "it means it scared me." so i said, "then just say that." and he knew i didn't want him picking up her way of speaking... perhaps i carry things a little far, but--iaint gun stop... haha!
You certainly don't carry things too far. I did that with mine. As teenagers they still picked up all the verbal drek and would use it at home from time to time and I would still do as you do. Three of them now speak well and the youngest, when someone says "what?" repeats himself in proper English, even when it's a kid with steel in his face.