Final answer:
The key aspect in a child's plan of care during fluorouracil chemotherapy is to ensure they maintain adequate hydration, which helps manage the side effects of treatment.
Step-by-step explanation:
The most important aspect to include in the child's plan of care when receiving fluorouracil as part of chemotherapy is maintaining adequate hydration. Chemotherapy drugs can lead to a number of side effects due to their non-specific action, often affecting cells in the body with rapid turnover like those in the gastrointestinal system. Ensuring the child stays well-hydrated is crucial to support their body's ability to manage the toxic effects of the chemotherapy, maintain renal function, and facilitate the elimination of the drug from the system.