The centre is for girls aged between 11 and 15 with the typical detainee 15 years old.
Sandow and Kelly both grew up in remote Aboriginal communities Sandow in Cherbourg, north of Brisbane; and Kelly in Katherine in the Northern Territory.
The pair told stories of how their lives could have been very different had they not had football to ground them.
Growing up in a small community there was always a lot of violence, so its easy to get caught up in it and get in trouble, Sandow said.
When I had the opportunity to come to Souths my mum sat me down and said: What do you want from life? Youve never worked a day in tour life. I said, theres always footy; and she said if I could put my mind to it, I could make it.
The 20 girls taking part in the session at Juniperina were all very interested in the boys lives asking questions about their hopes and dreams, and how they were able to achieve their goals.
Its tough and its always hard work, but if you want it enough, you can do it, Kelly said.
You know, your friends want to go out and party more and it can be hard, but you have to be disciplined.
Sandow agrees the structure and focus of football training gives him extra motivation.
Getting in trouble for disciplinary reasons really opens your eyes and makes you want to knuckle down and work harder, he said.
Many of the girls in the Justice Centre already have children of their own, and Sandow says he used his own children as inspiration to stay out of trouble.
I had my first kid at 18, and being a young man turned into a father, looking at him I have to do the right things and set an example for myself, he said.
Its a message both Kelly and Sandow hope the girls at Juniperina will follow.
If us coming out here today can help even just one of the girls get on the right track, then thats really rewarding, Kelly said.