hinhinmummy,
It's glad to hear your son has been undergoing treatment. Hope the waiting time for services available at Heep Hong and government is not long.
I have been the bookfair last two nights. The first night was OK; however, yesterday was terrible. There was a long queue moving slowly from the bridge near the MTR station towards the Convention Centre. I spent around HK3200+ for my girl. Some are AV materials, others are books for her and books concerning parenting. In fact, I still want to buy one thing and subscribe a journal/magazine. But I feel guilty to leave her at home again for another day.
Lastly, I would recommend you to have a look at "優質教育基金" counter at 5D 29, 31(Hall 5). There is some materials/resources for parents who have children like your son.
Hope you and other mama at this topic have a good day there!