personally

i prefer

1. rhymes,

2. short and simple words,

3.rhythm (such as in possible alternate unstressed and stressed syllables)

like the one i wrote yesterday for my 徒弟：

a little birdie flies in sky

sometimes low and sometimes high

when low, he picks at peach and pear

when high, he nibbles tasteless air

 

please notice alliteration in line 3

by the way, i am not sure if this is a 儿歌，because i seldom read a real 儿歌 by a native speaker, ha

'我感觉topsy.turvy语言功底也很好，他的遣词造句精炼，逻辑思维也很强。', true, that's why we should 对他更要严要求， haha