All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.
There is nothing wrong with writing a verse or verses of the Noble Quran in children`s books as long as the books are respected and the children handle them respectfully. Long ago, verses of the Quran were written on wooden boards to be taught to children. Today, children`s school books include and should include verses of the Quran in order for the children to learn them. However, children should also be taught how to respect and honor the Quran. And Allah The Almighty Knows Best.