You are right about staying away from corn, so what about the rest?
Flax seed is a great source of omega fatty acids, and isn’t truly considered a grain. Rice and barley, as long as they are straight up human grade rice and barley are more acceptable than corn. However, your sweet kitties are carnivores and don’t need any grains at all – grains are added to cat food for calories and to make the kibble stick to itself. Grains are really not something a cat needs to eat at all, ever. Grains cause kitties to become overweight and to shed – grains work like donuts to our cats – make them plump without any real nutritional value.
If your kitty will eat canned food, it is much preferable to the dry. The Wellness line has some grain free options that might work great for your baby.