It can't be 100% candidate (child)-driven. This process, esp. for those who are not insiders or not in the military, is byzantine, confusing, protracted, at times nonsensical.
There is no way on earth that a child -- yes, I'm deliberately using that term; a 17 year-old is, under the law, a child, and is not just de jure but de facto incapable of managing this process on his/her own -- can navigate successfully a process that baffles even sophisticated adults.
So the balance between parent and child is maybe 25% parent, 75% child overall. Or maybe 50/50 at the outset, gradually declining to 25/75, but it will never be 100% applicant/child-driven until the child is a (legal) adult and fully into the service academy or ROTC program.
My $0.02... YMMV.