Yes, this is something people are lenient about: lying to children. Lying to children is not permissible; neither to adults nor to children.
Tag: lying
Lying to children-1
Is it permissible to lie to a child of six years of age for his benefit and [also] to discipline him?
True essence of honesty
The true essence of honesty is that you remain truthful in a situation where nothing would save you except lying.
Beware of speaking ill of a believer!
...and whoever says about a believer something that is not true, he will be made by Allaah to dwell in the putrid fluid flowing from the inhabitants of Hell until he retracts what he said.
Lying for the sake of Da'wah
Is it permissible to lie for the sake of da'wah to Allaah?
The people of truth do not lie
By Allaah, we would never lie, and nor do we know what lying is.
Lying for real or as a joke
It is not befitting to lie for real or as a joke, and nor for any of you to promise your child something, and then not to fulfil [your promise] to him.
Lying without intending to lie
Is lying without intending [to lie] prohibited?
Reflect at the wisdom of Allaah
And look at the wisdom of Allaah and His love for the coming together of the hearts [of the believers].
Narrating fictitious stories
I narrate fictitious stories to children, and that is to encourage them to pray and be truthful, and all good things [in general]; so is this considered to be lies?