Assuming you're doing Canada-China-Vietnam and then Vietnam-China-Canada, you can enter China on a 72-hour Transit Visa Exemption. I believe you apply for and receive that at the airport after you arrive in China.
When you say "a day's work", do you mean working remotely by laptop over the internet? Are there any specific online services that you require that might be blocked in China?
Have you researched the transportation from the airport to the city?