Couple of points though - be aware you will have to get up very early like 5am ish to clear customs prior to disembarkation (US Customs not Disney's idea !)
If you need a visa to enter the USA, then you will also need it for a cruise; as yuo transit the US. If you can enter in VWP then you don't need a visa.
If you travel to the US on the visa waiver you just use your passport when you go on the cruise. They take non-US passports and keep them while you are on the cruise - they give you a receipt and you use your cruise card to get on and off the ship at any ports.