Randy, yes mindfulness training is connected in that it ties the breath to the focusing power of the brain when it is in the calming branch of the nervous system. That is, we are able to be more mindful when we are not in fight/flight or freeze. The excess CO2 has to do with the body’s interpretation of our surroundings as dangerous and that it is no longer nourishing for our body, which needs O2 for life.
I’m always happy to talk about teaching children to pray! A very simple approach is in the book Sleeping With Bread. Simply, look over the day for 2-3 experiences that stir gratitude/playfulness/happiness in the child. Have them say them aloud and after each one say, “God, thank you.” Then look over the day for places where they felt sad/fear/pain/grumpy. After hearing them say, “God, help me.” If you want to join in the sharing of your experiences (obviously adapted for children’s ears), then you can amend the response to, “God, help us.” This prayer form is based on the Examen from the Ignatian Exercises. If you would like other options and ideas, feel free to contact me through my website www.EmergenceInitiatives.com.