Hello, Josh,
As a family of five, we have been in similar situations wondering how comfortable we would be in a single resort room.
Disney's Caribbean Beach Resort rooms are 314 square feet. For us when our children were younger, we didn't feel cramped in a room of the same size. However, we did outgrow the room once our youngest became too tall to sleep in the extra bed. If you do a search on Google images for
Disney's banquette bed, you can see what the bed looks like and make a better guess of how well it would work for the child who will be sleeping in it.
If you are concerned that it may not work well for your family,
The Cabin's at Disney's Fort Wilderness are around 504 square feet and the family suites at
Disney's Art of Animation Resort are 565 square feet and at
Disney's All-Star Music Resort they are around 520 square feet. All of these resorts will have extra sleeping space, too. You could also book two connecting rooms at any of the resorts. A
Special Offer might also be available to provide you with a discount at a Deluxe Resort or Deluxe Villa Resort that have larger rooms.
I hope this helps to answer your question. If you have any further questions, please let us know.
Wishing you a pixie-dusted vacation!
-Kara