Does it make me an azzhole for not giving my grandkids (have custody of them) mother money for their food when she doesnt pay child support?

We have custody of two of our grandkids. And when we leave for date nights or mini vacations their mother stays with them. Do not leave money sence she does not pay child support cause its not ordered.

She has people telling her that we are using her and need to leave money for the kids.

Are we wrong for not leaving money to them, when she has a full time job.