"Thought I'd start doing some things for cancer awareness, and my agent came up with this idea," Miley said. "It's good to do, gets some kids out here and it was a pretty good turnout. Had a good time."
Miley's friend, Johnnie Santangelo, was diagnosed with brain cancer, which spurred Miley to help with cancer research.
Miley said Santangelo has been doing well lately, and he will throw out the first pitch before the D-backs play the Indians at Chase Field on Wednesday.
"He's doing great," Miley said. "He's actually out here right now going through some doctors' appointments.
"[Throwing out the first pitch is] something he's looking forward to doing."
The camp lasted about two hours and concluded as temperatures on the field began to rise. Fitness trainer and former Arizona State University softball player Felicia Romero led the campers in warmups, and from there, they split up into three rotating groups that moved between drills.
Miley led the participants in pitching drills in the bullpen of Field 3, preaching balance and throwing strikes.
At the end of the camp, five campers were named "Campers of the Day," and each departed with a bat signed by Miley.
"Everything went smooth," Miley said. "There was not a lot of sitting around. We did what we had to do, and that was it. It was good."
Miley said there were no plans for another charity camp, but he didn't rule out holding another one in the future.
"We'll see what happens," he said. "I'm sure we'll do another one sooner or later, but no timetable."
Adam Lichtenstein is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.