Frankly speaking there’s no need to teach children address ‘India or Bharat’ as ‘Bharat Mata’. And whosoever suggests to the contrary, can be ignored.
Why? As the Constitution of India nowhere defines India as ‘Bharat Mata’.
If the Constitution of India is the paramount book guiding India, then there’s no reason why the country is addressed in a way other than the way the Constitution prescribes.
Teaching children to humanize the Nation means limiting their perception of a Nation.
Nation is a comprehensive concept — mother land for one person, may be a beloved for another. It may be a Nation State for yet another.
Children are too young to be indoctrinated by such concepts as Bharat Mata. Ideally, they should be allowed to read about country in civics or polity terms. If as adults, they choose to call the country as mother, then it’s their decision.