Subject + "có" + statement + "không"? is the Yes/no question structure in Vietnamese. Without the word "có" the sentence becomes grammatically incorrect (which happened quite often in daily conversation, sadly). The word "có" here doesn't emphasize the statement!
Still don't understand why this is the plural you. It's ok when they go from Vietnamese to English - you can clearly see the Các bạn - but when they go from English to Vietnamese, how are we to know they mean ALL OF YOU or just you?