I don't think we used a specific packing list for someone for a child of DD's age (she was a young 3 when we went in Sept). We just used one of the generic packing lists on the web for Disney that was at the top of the google search.
I did opt to use pull-ups instead of underwear in the parks. While DD has been solidly potty trained for 6 months, we did not want the preassure of being in long lines, looking for bathrooms, and having accidents. The good news is that she made it through the entire trip without an accident, but the piece of mind for me by having her in pull-ups was worth it.
I also would not bring life jackets for swimming, as the resort pools on property have them there if you are staying on property.