HK Trip with a child

We are travelling with a 5y.o. son. He needs to have his own AE Travel Pass, i assume. Is the price of the going to be different?
And if we top it up with additional credits for use on Day 4&5 of out trip, will it register that the user of the card is a child hence will deduct child fare rate?

Helpful article by the way. Thanks so much!