Anyone can do the dining plan. Not all reservations can include the dining plan.
DVC reservations using DVC points can add the dining plan.
MYW package reservations (meaning a MYW room + Ticket combined into a package) can add the dining plan.
AP discounts are for room only reservations and therefor not eligable for
DDP.
AP holders can book a regular MYW package (so no ap discount) with whatever deal is out there for packages and book a one day ticket for each person in there party (so add about $70 per person) so that they become elligable for the dining plan. Then being sure never to use their room card to enter a park, that one day ticket never expires and can be used towards the purchase of the next years ap (must be at Disney to do this I think). Many ap holders have found this a good route.
Are you sure that the ap is the best way to go? For trips shorter than 6 days, it isn't always the cheapest ticket and the ap discount may or may not be the best deal.
10 Day no exp base ticket is about 400 (so think 2 5 day trips)
10 Day no exp hopping ticket about 435
AP is 462
10 day no exp hopping, water parks & more is about 478
PAP (ap with water parks) 595
The latest ap discounts were $36 at mods, when the
AAA discount was 26.25 so that meant the ap was only better by about $10 per night (less if you are talking a preferred location). There wasn't a value resort discount and only certain deluxes were discoutned, however those wer much better savings than AAA.
Anyways I'm just saying that if they like their package and are getting any kind of deal on it it may turn out just as well as their ap or close enough that it isn't worth the bother for now. I'd leave the package alone till ap discounts are released and you can really money compare what you are getting.