We occasionally travel with our 15 y.o. special needs daughter who is tube fed enteral formula, including Pediasure, via a Mickey button implanted in her abdominal wall. In her case, the Pediasure is a medical necessity. And some people drink this stuff orally as a nutritional supplement or meal replacement.

When flying with our daughter, we several cans of Pediasure on board and FedEx additional 24 can cases as required for the trip to our destination hotel. So far no TSA questions other than to verify medical necessity (which is self evident if you meet our daughter).

I understood the OP to be trying to bring the Pediasure as part of her carry-on luggage for her toddler who is not traveling with her. In this case, I suspect that the OP would need to establish at the checkpoint that the Pediasure is medically required for herself or plan on checking the Pediasure as baggage. BTW, the cases of Pediasure are packed for shipping - we use FedEx rather than checked baggage because it is just more convenient for us to have the formula waiting for us at the hotel.