As a chinchilla parent, you already know how sensitive these animals can be when it comes to their digestive system. That is why they cannot go long without eating, either. Leaving your chinchillas alone for several hours, but with plenty of food, would not be a problem.
Be aware that a chinchilla cannot go more than 24 hours without food or water. If they remain unfed for longer than a full day, the chances are that they will get ill and eventually die. For that reason, make sure that your chinchilla eats regularly and adequately.