Instead of a total artificial salt substitute for recipes which will affect the leavening, try one that has a lower sodium so it will still leaven without adding tremendous sodium amounts. Sweeteners will enhance the taste of salt. Serve a lot of pastas since these are most often fat free and therefore free foods for the diabetic. They are empty calories and entirely safe. They can eat a lot without getting sick and you don't have to worry about them leaving the table hungry because they are worried about diets and exchanges.
Vegetables are another good choice.
Fresh vegetables for salads or steaming are a great free food. No fat, more empty calories. Delicious and filling without being detrimental. Buy everything you can with low fat contents. This will make it easier for them to enjoy themselves eating without worrying about their blood sugar.