Percy explained that it's a charity Narcissa Malfoy is involved with. He covered the info from the invitation he'd received, but also mentioned the fact that Narcissa told him how she looked forward to showing him that her charity work wasn't a false thing, when he'd simply asked for more information on how to get involved... which was a little weird. It's not a trap. Right? Definitely not a trap?
Percy reiterated that he's hoping to build connections with that particular crowd - a task that's proven more difficult than he anticipated, the Weasley name isn't exactly opening doors lately - and mentioned that he'd be sitting with the Malfoys at their table. :/