I don't know if it's online. Last time I met a yoga teacher named Tang in Taiwan Province, she published a book about parent-child yoga, and adults and children can do it together, which is safer.
You can search online first, if not, you have to see if there are any for sale. There should be a CD in it, so you can follow it. I've seen some. Yoga that children do is not too difficult, but it is good for their health.