This is the 13052nd most frequent Russian word.
малышей
"Малышей" means "little children" or "toddlers" in English.
In this sentence, 'малышей' is the genitive plural form of 'малыш', a noun meaning 'little one' or 'baby', showing possession or concern for them.
Мы заботимся о малышей в детском саду.
We take care of the little ones in the kindergarten.
Here, 'малышей' is in the accusative plural, indicating that the action of playing is performed by these little ones.
Группа малышей играла во дворе.
A group of little ones played in the yard.
In this case, 'малышей' is in the accusative plural, functioning as the direct object of the verb 'увидел'.