Based on the definition, why is flatter not the best word in the sentence below?

"I have always admired the work of the children who fought for civil rights in the 1950s and 1960s, so I wanted to write a poem that would flatter them.”

It is too formal and fancy for such a simple and casual sentence as this one.
It does not show that the writer is giving enough praise to the children.
It is not a word that should be used to describe children.
It does not mean to thank in a way that an admirer would thank someone.