The saltshaker is inconsistent with a reduced sodium diet. Many people reach for the saltshaker by habit, without first tasting their food. For an elderly person, this might equate to a lifetime of learned behavior. Habits can be broken. Many foods taste perfectly fine without added salt.
Salt substitutes are widely available. You should use them with care, however, since they often contain potassium, which is sometimes itself restricted. Better flavor-adding solutions are lemon or lime juices, chopped onion or garlic, herbal mixtures, and ground pepper.
Keep in mind that when the saltshaker is used, it becomes nearly impossible to monitor how much sodium (in milligrams) it adds to the daily diet. If sodium is an issue, it may be best to keep the saltshaker off the dining table (and out of the kitchen when preparing food).