By SARA VANDEN BERGE   Stephenville officials are bringing the mayhem back to Stephenville in May.   The 3 rd  annual Mother-Son Mayhem will take place from 6-9 p.m. on Thursday, May 7, at Stephenville City Park.     It will be an action-packed night of laser tag, food, thrilling games and monster truck madness!   “We will also have a DJ and there will be a glow-in-the-dark robot,” Kaley Barnette, the city’s special events coordinator, told Beneath the Surface News .   “It’s