Sorry to hear about the new complication.
When I left on my trip, it sounded like things were going well.
I don´t have any personal experience, but can tell you that you can carry any of the supplies he needs onto the plane with you. They wont count against your baggage allowance and the tube feeding solution is not subject to the TSA restriction of only 3 ounces of liquid. Check their website at
www.tsa.gov ; the easiest way to find what you need to know is to do a search for medications and that should bring you to the medication information.
Hopefully some with experience will post, but I can also tell you that some people have posted in the past that they had their provider ship tube feeding solution to the hotel for them so that they didn´t have to carry it. Some people have also used a high bed point to hook the tube feeding on, but in our experience, many of the head boards are screwed to the wall, so your safest option may be renting the IV pole.
You could also rent a special needs stroller (there are some companies lised in the disABILITIES FAQs thread. If you are able to get one of those with an IV pole attachement, you could possibly park the stroller next to the bed and have the pole on the stroller do double duty. I have seen people doing feeds all over the parks (bolus feeds and continous feeds). You can store any solutions and supplies at First Aid at any of the parks.
Even though it seems overwhelming right now, in a few weeks you will be an old hand at it and things aill be much more settled by the time you go to WDW.