Don't want to burst your bubble but what you're describing is more the role of a Child Life Specialist than it is that of a nurse.
Working as a nurse in peds oncology, you will NOT be viewed as a friend by many of your patients. You're the mean person who gives shots, makes them take yucky medicine, puts tubes down their noses, holds them down to access their ports or for lumbar punctures, etc. Basically any patient under the age of about 5-6 will view you as a very not fun person. I have a 2 year old patient who cries the minute he sees me because he associates me with shots.
Peds oncology is a great specialty, but a tough one. It's hard to admit a kid at 2 am from the ER on the worst day of their parents' lives and try to comfort the parents when you know, because you've seen it so many times before, how this will end for them. It's hard to look into a devastated mother's eyes and listen to her ask you "WHY ME?" The reality of pediatric cancer is that many of these children die... for some specific cancers, there are almost no survivors. It's hard to make any one in the room smile when they've just been told that the only child they waited years to have will likely be dead in the next few months. When I worked in neuro-onc, several times a year, we'd get a patient who came in with some vague symptoms... headache, slight weakness on one side, head tilt, etc, MRI would reveal a diffuse intrinsic pontine glioma (a tumor which no one survives) and the next day, we'd be sitting in on a meeting where the neuro-oncologist would tell the family that their 6 year old (who they thought just had a lazy eye) is going to die in about 9 months. And it's devastating to watch this child's life unravel on your watch... to have a child who comes in walking and talking lose the ability to do absolutely everything before he ultimately loses his life.
Now, I've been working peds oncology in some manner since I became a nurse and I admit that I am jaded. I began in inpatient neuro/neurosurgery/neuro-onc and now do pediatric home care with primarily oncology patients. Most of my patients have ALL and I have several with neuroblastoma as well. Peds oncology nurses are people that no parent ever wants to know. Once they do know you and once they've adjusted to their new normal, you will be a friend to them and possibly to an older child (the younger they are, the harder they are to win over although teenagers can be especially challenging at times- they're my favorites though)... you will celebrate with them when they finish their treatment and cry with them when the battle is lost.
If you really think this is what you want to do, I recommend trying to get your preceptorship on an oncology floor. Then you can REALLY see what it's like.