Washington Kastles player Serena Williams had plenty to celebrate Thursday night. She won both her doubles and singles matches earlier in the day, sealing the 21-16 Kastles win over the Sacramento Capitals before a sellout crowd. There were also some very special guests in the stands — first lady Michelle Obama and first daughters Sasha and Malia, who chowed down on shaved ice while taking in the entire match. Williams later showed up at the official Kastles afterparty held downtown at the newly opened Lincoln Restaurant. Williams came in around midnight wearing jeans, sneakers and a loose-fitting, printed halter top that showed off her belly. She sat at a table in one of the restaurant’s private rooms and requested not to be bothered by the reporters and photographers hanging around. (Redskins running back Clinton Portis was at Lincoln at the same time, sitting in a nearby booth.) Williams later slinked outside to one of the outdoor tables so a female friend could smoke a cigarette. We caught her leaving with her friend after 1:30 a.m., heading into the Thomas Circle CVS.