Sure, knowing how to differentiate between safe and unsafe foods is important to teach a child with allergies. You certainly cannot do that before you’re old enough to read food labels though. And Halloween candy is usually not individually labeled anyway, it’s sold in large bags, with the ingredients listed on the larger bag, but not on the individual pieces of candy. Plus, even something typically safe, becomes unsafe if it is served in a large bowl of other allergy containing treats.

Also, how do you propose that a two or three year old pick candy out in the first place? It’s not like he can stick his hand in the bowl of foods he’s allergic to.

Also, I think you mean coddle and not cuddle. ‘Coddle’ means to treat in an indulgent or overprotective way. To be overprotective you have to be protecting the child in a way that is excessive or unnecessary given the situation. Since a child with food allergies can die from coming in contact with their allergen, and since a three year old cannot read for themselves, it is not overprotective to provide them with allergy friendly foods until they have the skills and maturity to pick out their own foods.

And lastly one of the absolute worst things you can do for a child with food allergies is train them to eat familiar looking foods or go off of the picture or look of the food since similar foods can have different ingredients and even the same food processed in different facilities can have different ingredients. You want to teach them instead to never accept food that was not given to them by a trusted adult who knows their allergies.