This is a superb site for finding downloadable podcast for kids to learn Mandarin. Not all the resources are free, but there are lots of really useful resource that are, including over a hundred audio files lessons and for learning pinyin.
http://ictmagic.wikispaces.com/Mandarin+%26+Chinese+culture
The thing that worries most non-specialists teaching language is pronouncing words correctly from a book. This is where Forvo is is priceless. Native speaker users and the site itself have uploaded audio clips of word for us non native speakers to copy. The site has 250+ languages uploaded. I tested the Mandarin section, as I understand that, and it was faultless. An amazing resource.
http://ictmagic.wikispaces.com/Languages%2C+Culture+%26+International+Projects
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