Be careful what you say about your kids, especially when they might hear you. Every time you talk about them their ears perk right up. They are listening to hear how you feel about them.
Only talk about your kids to other people when you have complimentary things to say about them. But be careful that you are praising their qualities, not just their accomplishments.
For example: Instead of saying “Jimmy won first place in the tournament”, say “Jimmy worked really hard to compete for the tournament. He committed time every day to learning his times tables and even asked his teacher for extra credit to practice. All that hard work paid off too: he won first place in the tournament. We are so impressed with his effort and dedication.”
Everyone needs to vent about their frustrations, and you should. But do it when the kids are in a different location all together so they don’t accidentally overhear you and internalize what you are saying about them.