What’s more despicable than a band of overgrown tweens who throw their weight around on the playground, bullying smaller kids who can’t push back? Overgrown tweens who throw their weight around and mug people. With guns. That’s what happened this weekend when four young punks accosted a 68-year-old man in Central Park. The kids measured from four-foot-eight to five-foot-five in height, and brandished a knife and a gun. It was before sunset around 96th Street on Saturday, and the man handed over his phone and some cash. There is an upside to getting mugged by tweens with feelings of invincibility, though: They don’t know not to avoid celebrating in front of one of New York’s ubiquitous, crystal-clear security cameras.