This study enrolls patients between 5 and 40 years of age with a diagnosis of Ewing sarcoma (including Ewing-like sarcoma) or osteosarcoma that has progressed on or relapsed after upfront initial therapy. The purpose of this study is to find the best dose of a drug called cabozantinib (“the study drug”) to give to patients in combination with a routine chemotherapy drug called ifosfamide.