Polycarbonate lenses are the best, especially for children.
Typically,the impact resistance of polycarbonate lenses is 10 times more than ordinary plastic lenses.Therefore, often used in safety goggles, sports glasses, children's glasses lenses.
By the way, glasses lenses are easily to get broken, which is the dangerous hidden trouble for children.
As you can see, you'd better choose polycarbonate lenses for your kid.
I suggest you buying a pair of plastic lenses for your kids. Though plastic lenses may a little expensive, it worth the price. Because plastic lenses are lighter than glass lenses so that they are less likely to slip down the nose and they are able to sit on the nose lightly rather than leave indentations on the nose and distort the face. In addition, plastic lenses can bear a greater force than a glass lenses. Therefore, plastic lenses is a best choice for children.
Well, in my opinion, you can just choose Polycarbonate lenses which are well known to be safer and thinner but rather lack optical clarity. And it can be a good choice for your kid. First, you should know that Polycarbonate lenses are also known to be thinner and lighter than traditional type lenses. Polycarbonate lenses offer total protection from UV light and radiations. On the contrary, ordinary plastic offers minimum protection from UV light. If your kid use plastic lenses, you may need to invest in antiglare material to protect your kid from any harmful rays. So in my opinion, you should choose Polycarbonate lenses for your kid. And this kind of lenses is durable.