If you have previously recommended this thread, you should see a tick / check mark on the recommend button. Click the tick to undo the recommendation (the tick may appear to change to a cross as you do this.) If you added a comment with your recommendation, you will need to delete that from your facebook wall separately.
I'd say yes. But give clear rules on how long they can use it, for what purpose it is, and stick to it. They must learn that these devices are not just play (even though we use them for play), and that they are part of our everyday's life, much like TV 40-50 years ago, or a plow 300 or 400 years back.