The teaching materials of Hong En Children's Series are carefully designed according to children of different ages, and children of different ages have corresponding suitable teaching materials. For children aged 4 and a half, the following series of textbooks may be more suitable:

1. "Hello Teddy": This is a set of English teaching materials for children aged 3-6. Together with Hong En Children's English APP, it can help children learn English while playing. The teaching materials are rich in content, including daily expressions, animals, colors, numbers and other topics, so that children can improve their language expression ability in interaction.

2. Hong En Children's Mathematics: This is a set of mathematics teaching materials for children aged 3-6, covering numbers and operations, graphics and space, logic and reasoning, etc. Through the gamification teaching method, children can learn mathematics in games and improve their mathematical thinking and problem-solving ability.

3. Hong En Children's Pinyin: This is a set of Pinyin teaching materials suitable for children aged 4-7. Through cooperation with Hong En Children's Pinyin APP, children can learn Pinyin in interaction, master the rules and skills of Pinyin reading and writing, and improve their language spelling ability.

The above textbooks are designed for children aged 4 and a half, and can be selected according to their interests and needs. However, each child's situation is different and needs to be selected and adjusted according to the specific situation of the child.