I bought the devices for a boy who was 8 years old at the time. He raves about it because it is handy and especially because the range is very long. You have to have the battery management under control. It has also happened that when he "urgently" needed to use it again after a long time, it had to be charged first. "Where is the charging cable????"
His parents have also been allowed to use it. However, I wouldn't buy such a complex radio for a 4-year-old child - when he is older and can use it independently, something will certainly be missing and it will no longer serve him. That would be a pity.