I agree with above and file for FMLA. This will give you job protected leave to handle this. If you have sick time does it cover absences for children?
I would write back and apologize for the unexpected absence, reiterate that you called in making them aware of the situation and (if you are eligible) notify him that you will be starting the FMLA request process with HR.
If your boss was attempting to start documenting a tardiness problem, getting this approved as FMLA should prevent further emails or it may be viewed as retaliation/denial of rights.
Edit to add: FMLA can be taken in small amounts at different times called intermittent leave
I would write back and apologize for the unexpected absence, reiterate that you called in making them aware of the situation and (if you are eligible) notify him that you will be starting the FMLA request process with HR.
If your boss was attempting to start documenting a tardiness problem, getting this approved as FMLA should prevent further emails or it may be viewed as retaliation/denial of rights.
Edit to add: FMLA can be taken in small amounts at different times called intermittent leave