DaveL already covered the Zika aspects, so I'll just add this.
Microcephaly is a birth defect that happens to developing fetuses, not children. Your children were safe from microcephaly the day they were born without it.
Your question is misleading in two regards:
The title head of the question, combined with the tag, assumes that there's some age limit to who can receive this virus. There is currently no proven age limit for contracting the zika virus. http://www.cdc.gov/zika/disease-qa.html
It's transmittable through mosquitoes and sex. http://wwwnc.cdc....