Let's forget for a moment about the illegal entry, and lets look at what the effect of being separated from your family is................................
I was orphaned at 8, and spent the rest of my time in foster care until I ran away to live with my Grandparents the last year of H.S. Kids that are removed from their parents at an early age suffer from low self esteem, abandonment issues, and it can cause them to be afraid to have close relationships with other people. I know, because that is what happened to me. Through the help of some really good friends and a bit of counseling, I was able to exorcise most all of those demons and am now fairly happy and healthy.
However...........................I had one advantage that those kids on the border don't. Closure. I had attended my mother's funeral and knew that she was dead and I would never see her again. These kids on the border? They don't know where they are, where their parents are, if they will see them again, or if they are even alive. Stuff like that can really wear on a person, especially if they are a kid.
No. I don't think that separating the kids from their parents is either necessary or even a good idea because of all the mental damage it can do.