
Well, it is true that cinnamon contains something called Coumarin. The substance Coumarin is harmful in high doses as high and prolonged intake can damage the liver.
According to the Swedish National Food Agency, children's intake of the regular cinnamon you buy in the store (Cassia cinnamon) should therefore be limited to a maximum of 0.5 teaspoon per day.
Ceylon cinnamon, on the other hand, contains much less coumarin than cassia cinnamon. This means that you don't need to worry about consuming Ceylon cinnamon as there is a very large difference in coumarin content (about 2500 mg/100 g vs 17 mg/100 g).
Therefore, I recommend using Ceylon cinnamon in baking for children. To be on the safe side. However, there is no risk of eating more cassia cinnamon on a single day, it is a long-term high dose that is dangerous.
Please read more at the Swedish National Food Agency (search for cinnamon), they have a risk report on cinnamon, and in their report on food for children there are also guidelines.
/Elin
Licensed Nutritionist