The thing is, whilst we know that more sweets is the last thing that the twins need, it's not the fault of the sweets that they are overweight, it's the rest of their awful diet. You can't outrun your fork as the saying goes, but for a child, there is no issue with sweets once a week if the rest of their diet is decent and they get plenty of exercise. Look at kids in the 60s and 70s - we ate plenty of sweets and puddings and bread and jam etc but we also ate wholesome unprocessed food most of the time.