Hi there,
You may go to the Amazon bookstore to buy the book “Chinese for Beginners” by M. Wond. It tells you how to let your kids watch a lot of Chinese animated cartoons without any charge. It is a very useful book. You kids would be crazy for the videos recommended therein.

Hi, here is a Chinese language tool book, you can have a look:
http://www.digmandarin.com/courses/guide-to-key-mandarin-chinese-issues-textbook

And there are also some recommended textbooks, you can check our reviews to choose the suitable one:
http://www.digmandarin.com/blog?by_author=&filter_category=&filter-tag=textbook

Cheers!

For learning and remembering Chinese characters, may I also suggest the Chinese Blockbuster Series, a comprehensive and fun method to help anyone read simplified and traditional Chinese characters and pronounce them in Mandarin. The series goes beyond the ‘top few Chinese characters you need to know to get by,’ as people too often realize that they don’t get anywhere with such a limited number of characters. The Chinese Blockbuster Series is comprehensive and covers what is necessary to reach reading fluency in modern Chinese.

Thanks! These books are really interesting