Barracks. Segregate the men from the women. Segregate all children over the age of six.
Feed them well. Have all adults work on a truck farm, all food to go to their kitchens with the surplus going to food banks. Have all children attend school six hours/day, six days a week. Pay the adults 25cents/hour. Repatriate them ASAP.
Create a system of trustees to help coordinate, manage and police the illegals. Build a small jail at each facility for minor offenses that cannot be addressed through loss privileges or extra work details. Major offenses or repeat offenders mays be addressed through the Federal Judiciary.
You should be able to house, clothe, educate and feed them on less than $40/day.