That's actually funny. You want to abuse children by unauthorized publication [for profit, e.g. ads or solicitation for donations?] of their picture on an anti-child abuse Facebook page? Don't you find that hypocritical?
And, since it was copyright infringement to put it on a Facebook page, you want to know if it becomes not copyright infringement if you just put a fancy border around and then put it back on the same Facebook page? Wow!
Here's what you can do - get a consultation with a local lawyer there in western Louisiana and discuss this project and get some guidance on what is legal. You likely need to get permission from each child's legal guardian so you are not abusing the abused children, and do your own original photos so you end the copyright infringement.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.