Do I need to have a visa to Hong Kong? Do I need to get a china visa as well?

I'm a Canadian citizen. I born in Hong Kong, but my HK ID card already expired. I want to travel to Hong Kong in the near future by my Canadian passport. Do I need to have a visa to Hong Kong. Also, I will travel to Shen Zhen for a few days (my brother is in the hospital), do I need to get a china visa as well? If so, can I get it in Shen Zhen entry? Will they refuse my entrance? Or should I get it in canada?