If grace is a free unearned gift from God then even an infant can receive the grace that is given in baptism. Nothing needs to be done to receive it. The catholic notion demonstrates this best. But then, the early church had no idea of what True Christianity was.
Option B: Assume some kind of "state of innocence" protects your child until the "age of reason" is attained, at which point strive to induce a "conversion experience" via a complex array of societal and psychological pressure mechanisms. Oh, yes. Since we are hard-wired to respond to the pressures brought upon us by those we respect, you'll probably be able to induce such an experience -- but you aren't God, so the converts you make are less likely to be genuine than those God makes.
Charles Finney, the American pelagian, introduced a number of human psuedo-sacraments into the experience of the American church, such as the "altar call." He also denied original sin, and preached a form of autosoteriology through will power.