Kid's party at Van Gogo (Cascais). Open bar, with alcoolic drinks! What would you do?

Tomorrow night, I will take my 15 years old son to a party at the Van Gogo bar (Cascais). The parents of his friend offered their daughter the following gift. Invitation to all her  15 years friends at the bar with FREE DRINKS. Open bar to all who wants to have a drink, including alcoolic drinks. Am I a good father to take him there? Are his friend's parents wise enough to give such gift to a 15 years old kid? What would you do?