Here's a brief list:
Clothes - pack for all weathers. Day time it can be warm during, but mornings and evenings can get quite cold! So pack clothes that you can wear in layers so you can remove and add layers as the temperature changes.
No need to pack anything posh unless you plan on eating at one of the top WDW restaurants like Victoria and Alberts in the Grand floridian.
Cameras / video - make sure the chargers are OK for 110V AC
Toiletries - whatever you normally use
Medicines - Standard stuff like Paracetamol, Imodium, plasters, anticeptic, moleskin (for blisters). If you have any prescription medicines may be a good idea to get a note from your GP, especially if you need to get the same medicine in the US because some drugs have different names!
Suncream - even when it's cool the sun is still quite strong.
Hairdryers - again make sure they walk at 110V AC
Passport
Flight Tickets
Money - Travellers Cheques in Dollars can be used just like cash and are safer than carrying loads of cash. Also, make a note of your TC numbers and keep in a safe place separately from the cheques incase you need to claim new ones if you loose them. (Good idea to cross off the numbers as you spend them so you know which ones are missing and which have been spent if you make a clam).
Credit Card - Good for those big purchases or emergencies. Look at the Nationwide CC becasue they don't charge for oversees purchases so you get a better exchange rate.
Driving licence - If you are renting a car you need BOTH parts of your license if you have a photo one. Old paper version is just as good. Although the photo licence is good if asked for photo ID when using CC in shops etc.
Park Tickets
Guide Book - Brits Guide to Orlando by Simon Veness is the bible
Comfy footwear - You will be walking miles in the parks, so not a good time to break in those brand new trainers
Travel Insurance Details - make a note of emergency numbers etc.
Phone Cards - either buy before you go or get them in the US.
Can't think of anything else at the mo.
