Honestly if you are going in December like your signature says, I would skip the water park and more option because one waterpark will be closed for annual refurb and in dec it can be hit and miss with weather. Dec in orlando can be cold to chillly to warm to hot, hard to predict.
With that many days I would def. do the hopper since you will find days that you want to bounce around and hit your favorites.
In regards to getting an AP or not that really comes down to if you want to be in the parks everyday, if you are okay not being in the parks for 2 days then just get a 10 day hopper.
If you want all 12 days in the parks than go with the AP.
Reasons to get AP:
1. Free parking if not staying on property and have car
2. 10 percent discount at any disney owned stores in the parks, resorts and downtown disney
3. Shopping discounts at some of the others downtown disney stores
4. Some dining discounts, not a ton
5. Option to buy Tables in wonderland card for 75 (only for florida residents and passholders) which gives you 20 percent discount on food and drink (including alchohol) for up to 10 people at 85% of restaurantes on property and a few quick service in resorts.
--> this would be good for the amount of days you will be there and if you plan to eat alot of meals on property (especially the high end signature or character meals)
Plus, if you plan to go again in 2012 you wont have to buy tickets, alot of people get two trips to disney on 1 annual pass and go almost a year apart.
All you have to do is make the second trip as close to the expiration date, like have your last day of your second trip be the day or day before you AP expires.
Hope this helps.