What sort of food do you eat? Meat and veg, one pot meals ect?

Try looking in the Health Food isle in the supermarket for kids snacks - the gluten free/'healthy' versions are often much better for addatives than the standard versions, Get the plain honey teddies rather than the hudreds and thousands version.
Rather than premade sauce, top meat with garlic butter.
Drop white bread for wholemeal and try and get one with out preservative (a friend swapped bread and her DS fought it the first couple of days but she just stuck with 'this was all the shop had' and after a few days he stopped complaining and she never bought white again.

Google Aditive Alert for a goldmine of info.