I can only talk from the medical point of view. Usually the biggest problem and issue for patients and staff on childrens cancer wards is hygiene (and sometimes parents...) - kids there practically don't have any immune system while undergoing chemotherapy, so check with the hygiene and nursing stuff early in order to get to know the hospitals regulations what they want you to do. I suppose from your writing you have already done that, so you are fine. They may in fact make you desinfect your equipment before, wear gowns and/or gloves, etc., depending on what you exactly do - this is not complete nonsense. Some patients there need to live in a rather sterile environment.
AFAIK will interferences with most medical devices in use today not be a major issue, but that will depend on the devices used at this hospital. The (medical) staff will hopefully know.
Depending on the ward you may completely interfere with their - sometimes quite busy - working schedule. Best will be again to talk to the staff at the ward some days before and have an open ear...