Poor child and poor you. Not fair to anyone. Unless the mom is willing to make some changes at home, I don't see group care working out. If you have good communication, I would lay that out for her, let her know what your daily schedule is, and let her make the decision whether or not she wants to prep her child for your daycare. Give it a reasonable time frame to work, maybe even with a pickup option if he is crying for x amount of time, keep her informed, and then be done with it if it doesn't work out.

The fact that he is only there a few days a week makes it even harder to transition him in Mom needs to get with your program.