All fun and games at Arthur Ashe Kids' Day

As much fun as Alexandra Ketcham, 13, of Brightwaters was having Saturday at the U.S. Open Arthur Ashe Kids' Day, she couldn't help but wistfully remember last year, where she saw her all-time favorite: Justin Bieber.

That her idol wasn't Rafael Nadal or Kim Clijsters underscores the range of entertainment offered. Tennis is just the backdrop to the many diversions on hand at the annual children's event held at the start of the U.S. Open at Billie Jean King National Tennis Center in Queens, where tykes take over the hallowed courts, teen sensations sing pop hits and clowns juggle oversized tennis balls.

"We enjoy this so much," said Alexandra's aunt, Vanessa Newman, of Melville. The rainout of the morning activities at the 2009 event didn't put a damper on the memories. "Even last year, we had so much fun."

Little Skylar Ashnault, 2, with help from her older brother Parker, 7, took turns swinging at volleys from a tennis instructor at one of the practice courts. The two come from a tennis family, said their father, Mark Ashnault, of Green Brook, N.J. "My wife Dawn was a competitive player" who played doubles at a professional level, Ashnault said, and their hope is that the tennis gene was passed on to the couple's four children.

Meanwhile, Trevor Lai, 7, shed his dark sneakers and took to the court in bare feet as his father laughed on the sidelines. "They didn't want his shoes marking the court," said Kyson Lai, a police officer from Forest Hills. As Trevor's returns failed to make their way over the net, his dad shook his head and said, "Looks like he won't be seeded."

An afternoon music and entertainment program featured the Jonas Brothers - whose every sung lyric was matched by the screams of their fans. The Bryan brothers took time off preparing to defend their current ranking as the best doubles team in the world to play in the backing band in a rock performance.

As Andy Roddick played a match with a young audience member, actor Nick Cannon sat in the umpire's chair and taunted the ninth-ranked player by saying, "You lost to a 9-year-old!"

Sisters Nicole Drago, 14, and Michela, 13, of Woodbury, cheered loudly when the emcee asked who in the audience was from Long Island. Their favorite of the day's activities? Everything. "I think the performances," Nicole said, and Michela added: "And the athletes!"

Clutching a large tennis ball, Matt Kleiman, 9, of Rockville, Md., waited patiently to approach the star players gathered on court, and eventually Federer added his autograph next to the Nadal signature already on the ball. Matt plays tennis, but his real goal? "I'm going to be Derek Jeter," he declared.