I agree with AFR.
Call to see if any AP rates are available for your stay. If so, judge if buying an AP will be worthwhile for the room savings, especially if you are not staying long enough or frequently enough to meet the "break even" point.
If so, book the room and buy the AP right before you check in.
You don't have to buy everyone in your party an AP, just one will give you the room and meal discounts.
Beware - having an AP forces you to return to WDW over and over and over...