Wow, it is so interesting for you to make a pair of sunglasses for your kids out of cardboard. You can search online to find the solution. Or you can just make the easy steps of drawing the two lenses, two nose pads and some frames lines. Then you cut the shape out and use the glue to stick them together.
As a matter of fact, your idea is really interesting, however, it requires good skills and craft of making things you know? Well, first up, you should get to know what kind of frame will interest your kid and what he or she prefers. Secondly, you should look for some hard cardboard as the material. Next, you gotta draw the outline of the frame and carefully cut it off. Last, you should paint it and add lenses to it.
That is funny to ask a doctor for the make of sunglasses with cardboard, anyway, it is very interesting and it remind me about the childish story and lots of fun. I guess we can imagine the shape of the sunglasses then start. The structure of glasses is two circles with two legs, as well as a bridge between the two circles. We can draw all the shapes of them with pencil on the cardboard, and then start to cut it into our needed shape pieces of parts. Finally, we can form them together with glue. After that, painted some colorful coating or tiny decorations on that, the stylish and smart sunglasses are ready, that is easy! At last, I would like to recommend you not mount the lenses on it, because no needs, it used just for fun, and poor quality lenses will do harm to your kid's eyes and the cardboard material is too fragile to contain such lenses. Ok, just for your reference!