Adavosertib and Irinotecan Hydrochloride in Treating Younger Patients With Relapsed or Refractory Solid Tumors

Inclusion Criteria: * Patients must have had histologic verification of malignancy at original diagnosis or relapse except in patients with intrinsic brain stem tumors, optic pathway gliomas, or patients with pineal tumors and elevations of cerebrospinal fluid (CSF) or serum tumor markers including alpha-fetoprotein or beta-human chorionic gonadotropin (HCG) * Part A: Patients with relapsed or refractory solid tumors, including patients with primary or metastatic CNS tumors * Part B: Patients with relapsed or refractory neuroblastoma * Part C: Patients with relapsed or refractory medulloblastoma or CNS embryonal tumors formally classified as PNET (pineoblastoma, CNS neuroblastoma, CNS ganglioneuroblastoma, embryonal tumor with multi-layered rosettes, medulloepithelioma, CNS embryonal tumor with rhabdoid features \[INI1 intact\] and CNS embryonal tumor, not otherwise specified) * Part D: Patients with relapsed or refractory rhabdomyosarcoma * Part A: Patients must have a body surface area \>= 0.35 m\^2 at the time of study enrollment if enrolling on dose levels 1-5; patients must have a body surface area \>= 0.46 m\^2 at the time of study enrollment if enrolling on dose level 0 * Parts B, C, and D: Phase 2 Expansion: Patients must have a body surface area of \> 0.49 m\^2 at the time of study enrollment at the recommended phase 2 dose of AZD-1775 * Part A: Patients must have either measurable or evaluable disease * Part B: Patients must have either measurable disease or must b…