I work as a part time WDW
travel agent. I am currently planning a trip for a family made up of parents, 3 children ages 18, 14 and 9.
The CM I spoke with a few weeks ago said that if all of the children are under the age of 17, you will be able to get connecting rooms and it will all be under one reservation number. If one of the children is 18 - they cannot guarantee connecting rooms. I asked what do I do with this family because they want to stay at a value but need the guarantee of connecting rooms. She said they have to do two different reservations and the 18 year old is the lead guest on the second room. They were not too happy with the fact they are going to have to not only split the party but they are under two different reservations. It was more expensive but they wound up going with a suite at AOA to guarantee that they could keep the group together.
Of course you can probably call back, get a different CM and you might get different information.