Mindfulness is so important. Even more important than practicing it is talking about it and making people feel inadequate for not meditating. It is your duty as a parent to do the same with your kids. When they're not receptive because they'd rather have a different mother than you, it's time to force them using these techniques.
Threaten to take away their electronics, and that includes electricity. They'll be living in the dark if they don't learn to focus on their breathing.
Tell them you'll take them with you while you run errands if they don't meditate with you for 30 minutes. Nothing worse than being trapped in a car with you for hours on end, even sitting cross-legged and humming nonsense sounds for a half-hour.
Lock them in a room. Don't let them leave until they come up with their own mental mantras.
Convince them the only way for them not to be teleported into a black hole is to meditate with you. If they don't learn to do a body scan in a week they'll be sucked into a dimension where time ceases to exist.