As expected, the website of Air China is yielding results. They pretty much make it clear that they will either get you to your destination within "reasonable time" or refund your ticket:
9.2.2 [...] if we cancel a flight, [...] we shall, at your option, either:
184.108.40.206 carry you at the earliest opportunity on another of our scheduled services on which space is available without additional charge and, where necessary, extend the validity of your Ticket; or
220.127.116.11 within a reasonable period of time re-route you to the destination shown on your Ticket [...] without additional charge. [...]; or
18.104.22.168 make a refund in accordance with the provisions of Article 10.2.
and regarding the ticket refund they state accordingly:
10.2.1 If we cancel a flight, [...] the amount of the refund shall be:
10.2.1.1 if no portion of the Ticket has been used, an amount equal to the fare paid;
You can consider 3 things:
- While your business might be affected by delays and cancellations, you are in no position to claim losses for your business by those delays and cancellations - unfortunately. The best thing you can hope for is that you do not have to pay for a flight that you did not take.
- There are 48 daily flights with daily from Beijing to Guangzhou. I would consider changing airline, one might be able to get you there
- Delays and cancellations in Beijing are abundant. Even if your clients are coming in to Beijing and continue to Guangzhou on a very tight schedule, there is a reasonable chance that they will make the flight simply because the chance that the flight to Guangzhou is significantly delayed. After Shanghai and Istanbul, Beijing is the airport with the most frequent and severe delays in world among the major global airports. You actually have a more than 50% chance of a delay or worse. I know it's a gamble, but this is how it often works.
- If the person changes flights from an overseas flight to Guangzhou in Beijing, consider routing them via Hong Kong. The flights are more reliable and it might solve the problem completely. They can either take a (very short) connecting flight to Guangzhou or the train.