In this post i am going to share with some good stuff and resources to use with your children, so as a school teacher and an Origami artist i have been trying this art with my students over many years of teaching and it is always fun and interesting to them, whenever they succeed to achieve a crane or a butterfly 
they become the happiest kids on earth, so here i can share with you some videos On YouTube to start with your kids folding, you just need ordinary paper
The easiest fold: the fish
Another lovely folding to do
another very interesting website i started with few years ago :
you can find tons of videos dedicated to origami, i hope you will enjoy 