I third the Caribbean! We stayed there for 5 days and it was AWESOME! Free bus rides everywhere on the property and there's even the option of an adult night out at Downtown Disney! LOTS to do on the property! It was a blast.
Depending on the age of the kids and what you'll want to do, be realistic about how long it will take to see all the things you want to see. We were there for 5 days and only made it to two of the parks thoroughly and didn't spend enough time at one of them and barely made it to the 4th! Not to mention there is so much more than just the 4 main parks. There is downtown disney, the World Wide Sports complex, and more...so much more! Water parks, awesome hotels to visit...you name it, it's there!