Ah, well I thought you had expanded your definition, as your example was a toddler.
If infants have no capacity for knowing and choosing and understanding the remifications, then they do not sin.
But we have no means to know what passes through the 'mind' of an infant. We don't know if the soul is full formed and simply unable to fully control the synaptic switches to get it's point across, or if the soul is in development along with the body. For all we know there is a potential for sin within the womb itself. It cannot be proven in any event.
And the "all have sinned" Bible verse must allow exceptions and can not be used as a bludgedon to deny Mary her role.
Even if I grant that all infants are innocent, that then leaves no special role for Mary in that case. There is truly *nothing* in the Scriptures that suggests an immaculate birth for Mary, nor that she led a perfect and sinless life (in fact, Mary herself suggests the opposite)- For if that were to be so, there would be no need for Christ, as His Mother would have set the precedent before Him.
You never had to raise children and teach thme about rigt and wrong and teach them to unerstand the ramifications of their choices? They are not born with it.
Even if I grant that all infants are innocent, that then leaves no special role for Mary in that case.
The case of the infant or insane or retared person who does not sin because he lacks the capacity to do so makes the Bible's "All have sinned" a less-than-absolute statement. It allows exceptions.
Mary can be an exception. Mary can be without sin and not violate this Biblical passage because it is meant to apply to most every, but not all occassions and people.