Hi Michelle,
I recently had the opportunity to tour the rooms at the Caribbean Beach Resort, and found them to be spacious enough for my family of four. The rooms have either two full-sized beds or one king sized bed. They are approximately 340 square feet, and have ample storage. The Family Suites at the All Star Music Resort are basically the size of two rooms at the All Star (260 square feet) together. There are some great, very detailed pictures of rooms at each of the Disney properties on the independent website
www.allears.net. You can click on "accommodations" from the home page, and select the resort you are interested in to get a sense of the rooms, and help determine whether your family would be comfortable in one.
As for Caribbean Beach, I think that the resort is absolutely fantastic, with nine swimming pools and elaborately themed common areas. The Pirate Pool is amazing, and I know I wouldn't have to worry about my kids feeling cramped in a room, because we'd never be in it!
Have a wonderful trip!
Tanya