Hello, Tim!
My family is pretty much the EXACT breakdown of yours; there is no way our daughter would share the bed with her little brother. I hear ya'!
Thankfully, you'll be staying at Disney's Old Key West Resort, a truly lovely resort (our first Disney Vacation Club Resort stay) which will make this issue not an issue. :-) Take a look at this chart of
Room Types & Pricing at Disney's Old Key West; you'll be thrilled to see what my family has come to rely on...a sleeper sofa AND a sleeper chair in the living area of your villa. Woo hoo!
Our standard is that the older sibling gets the sofabed, while the younger one gets the sleeper sofa. No issues. (Some day, when the little guy is taller than his sister, it may be different. But for now? We're golden.)
Enjoy your stay at OKW! This is a great resort, and you are going to LOVE the size of your villa, the fully-equipped kitchen, your in-room washer and dryer (not stacked...a laundry room will be at your fingertips!), the master bath and so much more about the public areas of the property, too.
Send more questions as you think of them! We love to help!