alopecia areata (which eventually becomes Alopecia universalis) has been thought to have a hereditary factor but it's nowhere near as strong as male pattern baldness, the fact is we don't know if it does or not
i wouldn't worry about it tbh because AA is more treatable than standard male pattern baldness, adult stem cell treatments have been used to treat (i am wary of the word cure) children and have been presented with massive effectiveness, almost bald children have been treated and have come out the other end with full heads of hair
so sorry i couldn't give an answer because we don't know if it's genetic or not but as far as your child goes if the worst comes to the worst, early intervention and a good dermatologist/trichologist will go a long way in helping them keep their hair!