Donor Natural Killer Cells, Cyclophosphamide, and Etoposide in Treating Children and Young Adults With Relapsed or Refractory Solid Tumors

Inclusion Criteria: * SCREENING: Patients with relapsed or refractory solid tumors and without known curative therapy or therapy proven to proven to prolong survival with acceptable quality of life. * SCREENING: Patients older than 21 years must have a solid tumor considered by study doctor to be of the childhood cancer type. * SCREENING: Performance level as measured by Karnofsky \>= 60% for patients \> 16 years of age or Lansky \>= 60% for patients =\< 16 years of age. * SCREENING: Documentation of measurable or evaluable non-measurable disease. * SCREENING: At least one documented histological verification of solid tumor diagnosis. Can be from original diagnosis or more recent. * ENROLLMENT: Patient must have fully recovered (i.e. returned to baseline) from the clinically significant acute treatment-related toxicities of all prior treatments prior to beginning treatment on this protocol with exceptions of cytopenias resulting from persistent disease, hearing loss and alopecia. * ENROLLMENT: Performance level as measured by Karnofsky \>= 60% for patients \> 16 years of age or Lansky \>= 60% for patients =\< 16 years of age. * ENROLLMENT: Creatinine clearance \>= 60 mL/min/1.73m\^2 (calculated by 24 hour \[h\] urine collection or nuclear glomerular filtration rate \[GFR\] scan if 24 h collection is not possible) or a serum creatinine based on age and gender as follows: * Age, maximum serum creatinine (mg/dL): * 1 month to \< 6 months, male 0.4, female 0.4; * 6 m…