This phase I trial is studying the side effects and best dose of decitabine when given together with doxorubicin and cyclophosphamide in treating children with relapsed or refractory solid tumors or neuroblastoma. Drugs used in chemotherapy, such as decitabine, doxorubicin, and cyclophosphamide, work in different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells.