You do not have to wear hijab in front of them at this age. They are kids.
Once they reach about ten or eleven, you must observe hijab as they are non Mahram.

Sheikh i am a 16 year girl and a hijabi. But I have my cousins 7-8 years old. Are they my non mehrams too? And do i need to cover myself infront of them as well?

Mahram | August 11, 2017 11:51 am
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Can a father in law be a guardian n mahram to the widow of his son.Pls mention with refrence ofquran n hadith. And what if he allows her to stay in his joint family house With other sons n families .Are the sons of his daughter be mahram to that widow??
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My wife’s mother is a revert therefore my wife’s uncles (mother’s brothers)are all non Muslims. So are they mahram to my wife? Can she stay without the headcover in their presence ?