If you have a chubby face, you should not choose sunglasses with round frame. Because your face is round, you should avoid selecting of round sunglasses, you can choose the frame with edges and corners. The nose pads should be a little higher. For the color, you can choose dark red or black. These are my suggestions, you can have a try.
The sunglasses are produced for protecting eyes to against the sun, especially the UV rays. At the same time, the sunglasses become a fashion decoration. It not only can be used in summer but also in winter. There are many shapes of sunglasses based on different factors, the face shape can be one of it. Usually, the person who has a chubby face should select a pair of dark colored sunglasses, such as purple, grey. He/she can choose the sharp round frame instead of normal round frame, which can make the face longer and thinner.
Oh, chubby face is very lovely. So please don't regard it as a problem when you fill sunglasses. It is very easy for you to select one suit for you. As you have sound face, you can select sunglasses with square lenses. They will make you look cool. Besides, when you buy sunglasses, you should also pay attention to the color. It depends on the occasions you wear them. If you just wear it when you are on the way to somewhere, dark green may be the best choice. If you often play with your friends on the beach, blue lenses are very cool there. And dark brown would be better if you are driving.