As far as price goes, you'll pay an extra $25 plus tax per night for the 22-year-old at a deluxe. We have a 20-year-old, so I can relate. Also, it is often cheaper to get two rooms at a value and sometimes cheaper to get two rooms at a moderate than it is to get one room at a deluxe.
Our family's ages are similar to yours, and we're okay in a deluxe. We prefer to do that over All Stars because of the lack of amenities (good pool and location) and Fort Wilderness transporation issues. We visit AKL to eat and hang out, but I'm not sure I would choose it b/c the deluxe room is priced comparably to the Epcot resorts. With older children, you can't beat the proximity to Epcot and MGM and fantastic pool there.