My own children are 13, 11 and 8, and I am really not all that hung up on cussing. If they are telling a story and they swear when they get excited, I don't do much beyond giving them the side-eye or gently reminding them not to say that in mixed company. Swears are just words. I do not tolerate "oh my god", as it is affixed specifically with a deity, and I am foursquare against mocking someone's spiritual beliefs.