I have a g-tube dependent 4 year old son, and had posted this very same question here the first time we traveled with him to WDW!
You are able to take all the formula you need with you and they will not charge you baggage fees for it because it is considered medical supplies. We ended up just taking it all with us and checking it in as baggage. The formula weighs a TON, so I don't know about shipping it, as I think that would get extremely expensive.
When I posted, I was also told that you can work something out with your medical supply company to have supplies shipped directly to the hotel. For our next trip, I am definitely going to explore this option more because it was definitely a logistical challenge to lug all the formula to the airport and from the airport to the hotel. Other than that, we didn't experience any problems.
HTH!