I would try the putting the cheerios on the food and so what if that is all he picks out it will have the flavours at least or a bit of mashed potatoes or cheese sauce of the food. Over time he may eat some of the food too. To compensate putting 5 cheerios on the plates of the other kids is not going to make or break their meal either. No seconds of cheerios for anyone. I would also not allow the child to have just cheerios ever even if it means zapping a tablespoon of potatoes to give at snack - again even if he just picks out the cheerios to eat.