The Forward Roll
USA Gymnastics Coach Eric Klauss explains how to teach kids the forward roll. It is recommended to learn how to fall in any sport to avoid injuries.
When working with kids is very important to create trust and have them see you doing the exercise first. If they can see that you can do it then they will believe in you and will follow you. Never ask a kid to do something you cannot do, because if the kid gets hurt then it will be your fault by not leading with an example.
If you are not able to demonstrate then you need to have someone who can do it, so you can explain it better in detail and make sure they see you are there for them to be successful. If they feel you will not be there to help them complete the exercise then they will not do it, they might do it wrong over and over, and when this happens things can go wrong.