These are guided meditations that you can buy online that I recommend: 

Creating A New Now by Ann Webster    body relaxation, excellent , teens through adults

Energy Awareness Meditation by Sudhir Jonathan Faust   Guided meditation for tweens through adults

Learning the Relaxation Response: Benson Henry Institute Mass  Good for children 

Short visualization exercise:

General visualization for download

Play short visualization directly from website:

 

 

There are MANY apps that can be downloaded to smart phones. Here are links to recommendations. Some seem to be free but have charges for the tracks; read carefully!  Simply Being, Calm and Mindfulness all let you vary the time..   others may as well.

Healthline

The Daily Beast

The Independent  UK

Saturday Evening Post

Articles on meditation benefits kids and general

Mayo Clinic, "Meditation: A Simple Fast Way to Reduce Stress"

Lifehacker: "What Happens to the Brain When You Meditate (And How It Benefits You"

Introduction to QiGong

Discovering Qigong, the Five Treasures  DVD is an excellent introduction, short exercise