Perhaps I can suggest one reason. We try to limit our Son's use of our iPad by not giving him the pass code but even through we try to stop showing him the code he still works it out by watching us as we log on. I know we could always log on out out of eyesight but having a finger sensor would better. I can't understand why Touch ID was not included with the iPad Air. As soon as it does, then I am upgrading by replaving my existing 16 Gb iPad to one with more memory.
You should give your son an iPad. You can restrict what he uses it for pretty much to your heart's content.