This is a false dilemma. "He/she" was never even mentioned.

In the context of the article[0], other options exist like:

If your child is in the kitchen, make sure he doesn't touch the hot stove.

If your child is in the kitchen, make sure she doesn't touch the hot stove.

These sentences are no harder to read than if "they" had been the pronoun used.

[0] - and I really think what the author is trying to do is make the reader think of a different child with each bullet point. Not a single, unspecified four year old, and not a collective group of every four year old, but one unique four year old for each bullet point. Alternating the gender of the pronoun creates this effect.