I don't think it will work. For the TSA, they would be considered a liquid since they would not hold their form outside of the container. I checked and it appears the pouches are labelled as 3.5 ounces. To get through security, you are only allowed liquids of 3.4 ounces or less that in total will fit in a 1 quart ziplock bag. You could put a few of the pouches in your 1 quart ziplock and hope the TSA doesn't raise the issue of their being 3.5 ounces instead of 3.4 ounces, but do you really want to take the chance you would have to toss them at the security checkpoint?
Food for a 19 month old would not be granted the same exceptions as formula for a baby.