My experience says that you can use your chip and pin pretty well everywhere. For day-to-day cash, use your Debit Card, although find out directly from your Bank what the charges will be, if any. Use your Credit Card for larger purchases, in shops and when eating out. You should find plenty of "hole-in-the-walls" where you can take money out, and none of these devices have ever been known to ask for your passport !
You will, of course, need some money directly on arrival, so take perhaps £200-£300 in dollars. If you have an extra Credit Card or Debit Card, keep that somewhere safe, just in case of emergencies.
Are you hiring a car ? Difficult to imagine having a holiday in the States without one, and I am sure you don't intend to spend the whole 14 days in Disneyworld ! You will need a Credit Card, with plenty of "space" on it, as the car hire company will take a swipe when you collect the car.