Changing diets takes some time to make sure the food switch goes well for your dog. Since you have an 11 year old dog, with a sensitive GI tract the first thing I would do prior to making any changes is consult with your veterinarian. Discuss your reasons for the change and verify this is a good move for your dog. Once your veterinarian gives approval, you need to choose a dry food that is good for a senior dog. The first thing to consider, if there have been no problems associated with your current feeding system staying with what works is a good idea.
There is no hard and fast rule for changing diets. It's a matter of taking it slowly for your dog to acclimate from one type of food to another. During the process if the GI tract acts up, speak with your vet and decide if this is a good direction for you to continue.
If your dog has been consistently feed canned food, I would continue to support his feeding with some of the familiar food. You have your daily quantity and feeding time frames. At first feed 3/4 of the familiar canned food adding in 1/4 of the new food. Do this for one week. Week #2, feed 1/2 familiar canned food and 1/2 new food. Do this for one week. Week #3, feed 1/4 familiar canned food and 3/4 new food. Do this for one week. By Week #4, the transition should be complete. Knowing the age of the dog, I would consider stopping at Week #2 where you're feeding 1/2 of each type. Again, speak with your veterinarian before making any changes.