If you don't want to have to switch to a different resort entirely, the most convenient (and fairly inexpensive) option is for "Uncle Eleventh Hour" to reserve a standard room at AoA in the Little Mermaid section. The standard rooms are far less expensive than getting another family suite, and if you reserve a family suite in the "Lion King" section (which is immediately adjacent to the Little Mermaid section), you'll at least be nearby. He'd have privacy when he wanted it, and could easily stroll over and "hang out" with you whenever he wanted. Frankly, I'd see this arrangement as a win-win for everybody.
Otherwise, as others have said, you're looking at a move to another resort and potentially a huge increase in the cost of your room(s). If it is important for you all to stay together, some options would be: (1) 2 connecting standard rooms at a moderate resort -- this would require 1-2 people in your party to share a room with the uncle and you wouldn't have a kitchenette or living area, although you'd have more space than a value, plus coffeemakers, double sinks, fridges, etc.; (2) a 2-bedroom villa (with 1-2 people sleeping on a living area foldout sofa) or a 3-bedroom "grand villa" at one of the deluxe DVC resorts, but either of these will be quite expensive.
If one of your children is under 3 and in a crib, technically you could could all stay in an All Star Music family suite or one of the Cabins at Fort Wilderness Campground (they both sleep 6, + a "child under 3 in a crib," but it would be a tight squeeze either way: in the ASM suite, the Uncle and kids would all be sleeping on living room foldouts, and in a cabin, the Uncle and at least 1 child would be sleeping on foldouts/Murphy beds and you'd all share a single bathroom)!
