The Riverside County Sheriff's Department has decided not to seek prosecution of two high school assistant coaches who left six Orange County basketball players in the desert after they became rowdy on a trip home from Palm Springs. "The boys had been acting up in that van, and they were causing a danger to the coaches on the highway at the time," Sgt. Ron Dye said. "The coaches didn't really intend to abandon the boys, but just wanted them to cool off." Riverside County officers had threatened possible child-endangerment charges against coaches R. Lyndon Boop, 26, and Mark Kremer, 21. Returning from a tournament on July 18, the coaches left the six basketball players from Sunny Hills High in Fullerton stranded for about two hours in a van along Interstate 10, about 18 miles east of Banning. A sheriff's deputy discovered the stranded teen-agers.