If you are equipped with a children's mobile phone, it is necessary. At least parents and children can contact at any time, and there are functions such as positioning and asking for help, which are very practical, but these functions have no entertainment items, so don't worry about children's addiction to playing mobile phones.
But if it is an ordinary smartphone, it is not necessary. In fact, the most important function of mobile phone is communication function, and it is enough to use children's mobile phone.