An environmentally conscious downtown crowd turned out at the Ralph Lauren store in SoHo Friday night for cocktails and shopping in support of the Riverkeeper foundation, one of the beneficiaries of Polo Jeans’ G.I.V.E. campaign. Co-hosts Robert F. Kennedy Jr. and Alex Matthiessen, executive director of Riverkeeper, worked the crowd; Amanda Hearst, the current face of the G.I.V.E. jeans ad, gave endless TV interviews, and two of Kennedy’s six children ran around. But charitable acts weren’t the only things on people’s minds. As David Lauren earnestly explained his commitment to inspiring volunteerism in American youth, Kennedy interrupted to ask, “So I hear you’re dating Lauren Bush.” “I’m not,” muttered an abashed Lauren. “Well, I’d really like to meet her,” persisted Kennedy.