Something a young Chinese kid would read (5-10 years old).
I recommend some suitable story books for your children, it also can try to figure out how Chinese characters work and Chinese structures from very simple sentences, check this link, you will find a list of Chinese story books for whatever your need is! http://www.hanbridgemandarin.com/article/kids-teenagers-chinese-learning-tips/best-chinese-story-books-for-children/
- A Magic Paint Brush 神笔马良 (shén bǐ mǎ liánɡ)
- The Water Dragon 雨龙 (yǔ lónɡ)
- The Phoenix and the Hundred Birds 百鸟朝凤 (bǎi niǎo cháo fènɡ) ........
You kids will read Chinese story books better with a professional teacher’s guidance.
Here's one starting point: 我的第一本日记：二年级的美羊羊
I think it's part of a series of similar books called "我的第一本日记". It's a schoolgirl's diary but not a real diary, I think an adult actually wrote it. It's got pinyin printed above the 汉字.
I read it myself; didn't understand everything but I still found it to be a rewarding read. Makes a nice change from all the boring textbook material. It's probably suitable for Chinese kids 8 years old or upwards.
I admit this one is probably more for intermediate students than beginners, but perhaps there are others in this series that are easier.
For ages 8-10, I recommend 康軒(Brand) 國小學習(For Elementary level) 自修國語 (Self-study) level 1-3. These are books easily purchasable in Taiwan and are in traditional characters. It is important for ages 5-10 to read books that aid in pronouncing characters, whether it is pinyin or ㄅㄆㄇ (bo po mo).
It's pretty much the same teaching material as what they teach in school. Here is a link for the picture http://www.pcstore.com.tw/ibookhouse/M10148138.htm
People have different opinions on textbooks as a "reading material", but I personally think they last longer, has more stories, and provide a better value in the long run.