... I don't like washing when I'm on holiday ao I take enough underwear and clothes so I don't have to use a washing machine ( No, we don't travel light

!!)
I would add to the list :
NB - essential:
driving license of all those intending to drive the hire car
earplanes
bumbags - great for the parks for being hands free and keeping passes, cash etc close to you;
notebook with
reservation & PS conf nos, rough plan plus EE days and UK addresses for sending cards, I take the notebook in handluggage with full addresses of where we'll be staying - you need a full address for the visa waiver form.
if the children have an
autograph book from a previous visit, take that plus a
fat pen
insect repellent - be prepared! I was bitten on my first night so unless you are going to the supermarket straightawawy when you get there, take some with you.
camcorder battery recharger plus adaptor and spare cassettes for same!
disposable waterproof camera(s) for the water parks
if taking a young child, their favourite
toy(s)/cuddlies - they need something that is familiar to them in strange places
plus: Calpol and any other
medicines that your child may need: our son had a fever on our first visit and detested the taste of the Tylenol syrup
prescribed medicines
Dollar Travellers cheques
US Money for tolls