You have the advantage of being familiar with the hospital environment. Lots of us were absolutely scared to death on our first clinical rotation. Some of my classmates had never even been around a sick person - lol!
Starting with your BSN should be fine. I think Pediatric Oncology is a very rewarding area, although very emotional. Staff nurses bond very strongly with patients and families. Most kids do very well and end up having parties for their last chemo treatments. Others of course, sadly, do not do so well, and the staff shares their family's grief.
If you want to go into management, you need a good foundation as a staff nurse. I think managers who have never worked "in the trenches" have unrealistic ideas about how things really work. Also, if you're working, most places have tuition reimbursement. You can work for a couple of years, then go back to school part time for your Masters, on the company's dime. I didn't pay a cent for my Master's.
You don't have to be a nurse practitioner - that's only one of many areas you can get a MSN in. You can specialize in adminstration, or be a nurse clinician. However, you might discover after working, that you'd like to be a pediatric hematology/oncology nurse practitioner. They work with that population as both inpatients and outpatients, and do lots of teaching. Whether as a staff nurse or an NP, your personal life experience would bring a lot to your care, as the parents (and the children) are so desperate for hope when they're first diagnosed, and you would be that hope personified.
Don't worry about being bored in your CNA class. You will have the HUGE advantage of not being intimidated by medical terms or equipment, but you will still find it interesting, I believe. Plus, working as a CNA will be a great way to "get your foot in the door" of a hospital, and find out more about where you'd really like to work. Also you may even be able to get tuition reimbursement after 6 months of employment, depending on how many hours you work.
Good luck! You'll be a great nurse!