with shenzhen 5 day visa Can I visit guangzhoue

Sorry, you can only stay in Shenzhen with the VOA.

No, unfortunately, Shenzhen VOA is limited to just Shenzhen city limits. However, at Lo Wu (Luohu) border crossing you can apply also for an ordinary single entry tourist visa valid for 30 days and for the entire China, but the issuing time could be somewhat longer and the Canadian citizens are expected to pay 406 CNY in cashless form. You should just prepare rough itinerary and an accommodation booking confirmation for at least for the first overnight.

Could you tell pls the name of the authority or agency that issues that single entry tourist visa for 30 days in Lo Wu border crossing that you mentioned?

That is not an agency. This is an immigration authority of China right at Lo Wu (Luohu) border crossing. So, you can get one by arriving at the border crossing and applying for it in a very similar way as you would apply for a Shenzhen visa. This is a very convenient detail, although it is not exactly automatically granted as it is a Shenzhen VOA, but it will require some waiting time at the border before it is issued. Also, you should be prepared for an additional set of questions. Nothing to worry about because all the procedure is worth it because this is probably the simplest way how to obtain a single entry, regular Chinese visa valid for the entire country for 30 days. Of course, the price is higher, but again, definitely worth the effort and money.