if you want to work with cancer sick children, is there a job for that?

Pediatric Oncologists are physicians that deal with cancer in children. They can subspecialize further and deal primarily with specific types of cancers like Leukemia. Or, they can get into something like Pediatric Neurosurgery or Pediatric Oncology Surgery where they deal directly with removal of tumors rather than the day to day treatment.

Experienced nurses can certainly work their way up to employment in these types of fields. In the US, a nurse starting out will likely need an MSN or a BSN with loads of experience in the field.

BUT you don't have to go for those roles that require so very many years of training and top grades. Go and visit the place you want to work and ask around what all the people who are there do.. some will be therapists, teachers or helpers. Not everyone who works with sick children needs to be able to heal.

Good Luck

First you become a doctor or nurse. Then you become a specialist.