Girl: If you don’t mind the compound surname, you can try: Cao Qiu Chenghuan. Just call her Huan'er or Chenghuan.
Cao Yixin’s nickname is Xinxin, Yiyi, Yixin.
Cao Yuxi’s nickname is Yu’er, Xiaoyudian, Xiaoyudi, Xixi.
Cao Ruohan’s nickname is Ruoruo, Hairpin’er. (The hosta flowers bloom in August)
Cao Yingchu’s nickname is Ying’er, Chu’er.
The boy’s compound surname is: Cao Qiu Yinuo, nicknamed Nuoer, Yier.
Cao Sihan, (this name seems to be applicable), nicknamed Haner, Sisi.
Sorry, boy I just can’t think of a few. Hope to adopt it, thank you