You can search for "children's pinyin teaching" or "children's pinyin learning" on Mi Le, and find many video tutorials suitable for children to learn pinyin. In addition, there are many professional educational institutions and teachers offering pinyin courses for children in Tencent class, covering initials, finals, tones and other aspects, which are suitable for children of different ages to learn.
In the process of learning, please keep up with the children's learning rhythm and guide them appropriately, so that children can master pinyin knowledge in a relaxed and pleasant atmosphere. At the same time, the companionship and encouragement of parents is also very important for children's learning progress. I wish you and your children a happy study!