I don't think there's anything wrong, just might be a bit boring! Also natural rolled oats aren't fortified which can be good for young kids to have a fortified cereal. Tbh we used to alternate between ready brek (fortified fine unsweetened oats) and weetabix but now he's a toddler, I give him own branded versions of rice krispies, mini shredded wheat, shreddies, cornflakes (not very often, they have a bit of salt in them), special K (original version) etc. As well as pancakes, toast, fruit, yoghurt...