No kids should have unfiltered internet. Everybody thinks my kid is such a little angel, and won’t do anything wrong. Unless your kid has something physically wrong with him r”l, he or she will have a yetzer hara that can easily get out of control.
There is plenty for them to do without being on an unfiltered device. They will not die of boredom. Try books, hobbies, sports, chesed projects, etc.