I have included some websites that offer guided meditations and scripts.  They are helpful to use when your child is feeling stressed or overwhelmed.  

Calm App: 

The home page offers a free guided meditation.  If you wish to access more content, you will have to pay for the material.  It is 14.99 a month or 59.99 a year. 

https://www.calm.com/

Green Child (https://www.greenchildmagazine.com/free-meditation-guided-relaxation-scripts-kids/): 

Offers free scripts for guided meditation

https://www.greenchildmagazine.com/guided-relaxation-peaceful-butterfly/

https://www.greenchildmagazine.com/guided-relaxation-pausing-to-understand-anger/

https://www.greenchildmagazine.com/guided-relaxation-lakeside-meditation/

Youtube: 

Guided Meditation for Children- Your Secret Treehouse: https://www.youtube.com/watch?v=DWOHcGF1Tmc

Mindful Meditation for Kids- Breathing Exercise: https://www.youtube.com/watch?v=Bk_qU7l-fcU&t=153s

Guided Meditation for Children- The Gratitude Tree: https://www.youtube.com/watch?v=64QzBuhsyuk