Ian Schrager now knows what it’s like on the other side of the velvet rope. The Studio 54 creator went on Thursday to the University Club, where his daughter, Sophia, 15, and Sophie Lasry, her friend from Trevor Day School, were presenting Bill Clinton with a $20,000 check for Haiti relief, money they raised by inviting 300 friends to a benefit at Schrager’s Gramercy Park Hotel. But Schrager, unaware of the club’s dress code, arrived in sweater and jeans and had to buy trousers, a shirt and a tie at a nearby store. He did a Superman-like transformation in the back of his car, making it inside in the nick of time to see the check change hands. The proud father left smiling.