I had a little boy In my care like this and unfortunately it just got too much for me and had to terminate. The parents we not willing to help and would just laugh it off. He would not just seek attention but would scream/cry at the top of his lungs. Even wouldn't let me change anyone else diapers.
I agree with you as long as the parents are willing to help then it could work out fine. Sorry don't have much advice. Good luck and hope you and the parents can figure out something that will work.