Teaching children to cook is the best way to teach them to enjoy healthy food.
The best way to keep your children free from added sugar is not to give them any food or drink with sugar added to it! Like alcohol, sugar is an acquired taste, so if they never acquire it they will never miss it. As they get older you can explain all the health problems that sugar causes, including ugly decayed teeth and bulging tummies. Read Chapter 8 in Twenty-First Century Nutrition and Family Health to get all the ammunition you'll need to shoot down the Sugar Plum Fairy and the Hairy Boo. It's had some great reviews.
Sugar added to food and drink is a principal cause of obesity, heart disease, type 2 diabetes, tooth decay, and a number of other health problems. All the sugar our bodies require can be obtained from dairy products, fruit and other foods, but above all from starchy carbohydrates which the body converts to the kind of sugar it needs - glucose.
Natural foods and drinks do not have added sugar, so a liking for sugar is an acquired taste. Therefore the first strategy for keeping our children sugar-free is to prevent them from acquiring a taste for sugar in the first place. In other words, don't give them from birth any food or drink which has added sugar. They don't need it and it will only harm them.
However to be realistic sooner or later children will be given sweets or will buy them with their own pocket money. So parents need a strategy to limit the damage that sweets will cause, particularly to the soft enamel of growing teeth. Two possible strategies are (1) to ban completely the consumption of sweets and chocolate until, say, their 16th birthday, or (2) to give each child a sweet tin into which all sweets bought or given are put, and which the children may open only at occasional set times such as Sunday afternoons.
Or course, when your children are old enough you will have to explain to them why you are limiting their consumption of sweets and chocolates, and why it is so important to avoid any food and drink that contains added sugar. At the same time you yourself must practise what you preach.
The limited use of non-sugar sweeteners could be employed if necessary, although the long-term effects of using these regularly are difficult to ascertain. 'Sweetly stevia' is a natural, sustainable product of the stevia root that is not extracted using alcohol and leaves no bitter aftertaste. It's available from EBay and other stores, but is currently far more expensive than common table sugar (sucrose), and in my opinion it is better to learn to enjoy food and drink in its natural unsweetened condition.
Twenty-First Century Nutrition and Family Health will give you all the ammunition you need in your family's fight against sugar. It covers all the health problems listed at the beginning of this article, as well as mentioning other problems for children that can directly be caused by sugar consumption, such as hyperactivity, difficulty in concentration, general bad temper, anxiety, drowsiness, decreased activity and eczema.