This early phase I trial compares a new method for dosing vincristine in infants and young children to the standard dosing method based on body size in older children. Chemotherapy drugs, such as vincristine, work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. The same dose of a drug cannot be given to all children because they vary a lot in size from infancy to adolescence. The dose of most anticancer drugs is based on a measure of body size called the body surface area (BSA). BSA is calculated from a patient's weight and height. However, infants and young children have more severe side effects if the BSA is used to calculate their dose, so adjustments have to be made to safely give anticancer drugs to the youngest patients. A new method for dosing anticancer drugs in infants and young children has been developed that uses body size to determine the dose. Collecting blood samples over time may help researchers understand how the new vincristine dosing method affects drug levels in the blood over time in infants and young children compared to older children.