I don't agree with that CSPA age calculator you cited. This calculator does not apply to the PERM based I-140 case, but applys to the family-based and the other I-140 cases, etc.
I find one here which is more reasonable:
http://engnishimura.com/immigrant-visas/cspa-child-status-protection-act
Of course, you may use the Calculator you cited to file your child I-485 and then, let USCIS determine it. But if it does not work, you will not only lose the I-485 filing fee and physical exam fee, but also it will affect your child's future F1 status extension (e.g. transfer school, go to graduate school, OPT application, etc.).
