Just FYI , shipping alcohol via the USPS is prohibited. Since the USPS can't insure that it will be "received" by an adult of legal age, they won't accept it. BTW, it's done quite a bit and nobody inspects packages as long as they don't break open or look suspiscious (i.e., BOOM!).
Soooo, if you do it, don't tell the window clerk what's inside!