Buying child IC card at Haneda airport

Hi, I have read that the IC cards are only available at selected locations so we decided to get ours at Haneda Airport before getting on the monorail. We can get Pasmo passport or welcome Suica.

We will arrive at 20:30 so would probably be around 21:30-22:00 by the time we will be getting our cards. We also need 2 children cards so may not be able to get the cards from vending machines as it needs verification.

I have no preference on which IC cards but where would be the best location to get them before I catch my monorail? And from those that got them recently at Haneda, are both available?