Oh, Roy is your uncle?! All along I was under the impression he is your cousin. There is a chance that the other brothers never came to Canada due to financial ($500 head tax) or age restriction. But Canada angle is still worth looking into.
When was the raid? Sounds interesting. How long do they keep such records?
I wouldn't bet the family farm on finding any government records before the communist take over. And don't forget the destruction records and historic objects during Cultural Revolution. I don't have a birth certificate and I was born in Taishan just before the communist take over. The situation may be different in large urban centres such as Guangzhou.
The best bet would be seeking out the head honchos in the village and the clan. They should have records on your grandfather and his siblings. Depending on the contact your grandfather or his siblings kept with those in the village they might even have your father and his siblings' names.
I have a cousin, on my mother's side, living in Taishan. His village, Fu-Shi, is not far from Wong Hong. The distance is similar between Hamilton and TO. I can ask him to go and inquire if you like.