Everyone in the room has to have the same tickets on your package (but it doesn't have to be the same as your length of stay) and if you have the dining plan, everyone must have the same dining plan for the entire length of the stay, even if some are leaving earlier.
[Additionally, if you have more than 2 adults in one room, you will most likely be charged the additional adults fees for that - I think it is $10 (value), $15 (mod), $25 (deluxe) for each night per person. Not related to your question but it sounded like you might be talking about adults.]
Depending on your situation, you might do better to skip a package and book a room-only reservation and separate tickets, but then you cannot add the dining plan.