How the HUTONG card charged the metro service for the children (under 130 cm)?

Normorlly the children has the children ticket. So if they use the Hutong card , it will be charged with the children price automaticly or they will be charged the same price as adult if they use Hutong card ?
Pls advise ....or they no need to get Hutong but they should buy the children metro ticket at the counter or machine instead.