If your children is at primary level, they can start to learn 國際音標, otherwise, it is not easy for them to learn & remember all those sound & sounds. I will suggest you (parent) to learn it first, then teach your children. When they grow up, send them out to learn again. In China, there are many self-learning VCD for children but I never view it and can't give you a recommendation.
Derrek Kwok has a class for both parent & children during summer holiday. I guess he also has class for primary students.