The problem is there are only a few different solutions:
1. Release parents and children into the US regardless of legal status.
2. Keep children in jail with their parents.
3. Separate children by sending them back to their country.
4. Separate children by placing them somewhere in the US (either with family or social services).
5. Send the entire family back to their country they came from.
Keeping innocent kids in jail is not right. Separating kids is not right. Having open borders is not practical. Sending back people to their own country is not right.
There is no solution. Many people who make the same argument as you would say just let them into the US but it is not practical when you have a welfare system. Many who criticize the current system even Bernie Sanders [0] says you can't have open borders since it would cause too much strain with our welfare system.