Translation:My brothers and you will see me drink a lot.
Just to point out in proper English you would never say "My brothers and you..." it would always be "You and my brothers..." The person you are talking to directly (you) should always be referred to first, it is polite to refer to the people you are with before yourself or others who aren't there. I.e. You and I You and them
"Vão" is a form of "ir", "to go". You can use it to express the near future, just like in English. A more literal translation of this sentence would be "my brothers and you are going to see me drink a lot."
Why is, "My brothers and you go to see me drink a lot." wrong here. (aside from it being a silly sentence, like most Duolingo sentences.)
Because the more natural English phrase, and more consistent with the lesson, is "are going to see me" and not "go to see me." The purpose is to illustrate the use of "go" ("ir") to express the future. You're not necessarily incorrect, but there is a more probable translation.
Yes. Remember "Aquela mulher é muito bonita, mas é muito jovem para ele."? That woman is very pretty, but she is too young for him.