[Dave Marx]

There are a lot of pieces here...

A basic MYW package simply is a room and park passes. Is that the kind of package you have, or did you also add Disney Dining Plan?

You won't be able to "upgrade" your MYW pass to an AP before you arrive, because you don't actually have the pass. It's only activated when you arrive. You'll have to buy the AP separately (to get the voucher) - then you'll qualify for the room discount.

Let's leave all the other initials - DDP, DME, etc. on the side for the moment, since those weren't part of the original question. If it turns out that Dining Plan was booked as part of the package, that's a different matter.

If you got a free Dining Plan deal, then I suggest you keep what you have. The savings on the room with the AP discount will probably not come close to the savings delivered by the free meal plan.

If you're paying retail for the Dining Plan, it can also be purchased as part of an AP reservation.

Since there's normally no cost benefit to booking park admission as part of a package, the most likely way to do things is to:

a) Find an (announced) AP discount that justifies changing your reservation
b) purchase one annual pass per room you'd need to book (one AP for yourself, if you just need one room)
c) Call to change your reservation.
(Note that you may have to cancel the first reservation and await a credit of your payments, and put a new deposit down on the AP-discounted room.)
d) Buy retail park admission for those members of your party that will need it (you can do that when you check in at your resort - no need to "reserve" park admission in advance).