Hi - you don't say how old your baby is or will be but try phasing down to room temperature if he/she will accept this. Just warm a bit less every day but don't be to quick.
We always did room temp with my kids as I Brestfead, pumped as well as using formula. Since breast milk is room temp I just kept everything room temp and that worked great.
You can use ready to feed, or powder this way. Just carry baby bottles with the water and add the powder, carry powder and add bottled water or carry ready to feed.
Be sure and check out the baby care centers at every park. Lots of supplies and a nice place to change and feed baby and stay cool for a while. They also sell a small variety of items in case of emergency.
IIRC after a week or two unless your baby has issues you won't need to steralize - check with Dr of course. Just be sure and clean with hot soap and water. Bring along some dish soap and plenty of bottles and nipples with some sort of drainer and you should be ok. Most disney hotels do not have any kitchen facilities - unless you go with a home away from home option.
We used the playtex bottle system - this will keep down the bottle washing, I loved the drop in kind.
TJ