My daughter works for Duchess of Kent Children's Hospital after school and holidays for few years. It is fun to teach and play with children. She always collects and gives books to children. They smiles at all times even in suffering. Volunteer job is a service to our community, not an advantage ticket to be a doctor. Please encourage your girl to understand the people who work and live there, especially she may have a big heart to be a good doctor.(tough job).
Your can call the hospital and maybe other small hospitals like Tung Wah Group, and ask. When committing the work, please make a regular visit continually because once the children know you well, they would be looking forward to your visit. Please don't break their hearts.
The drawback is this hospital located at a not easy to go zone. you would need to arrange the transportaion.
p.s. my daughter is good at take care of people, but not make a career at hospital.