My suggestion is to forget about Disney and concentrate on Universal. I know that probably sounds radical. I am assuming that since you have done Disney four times your daughters are teens--or pretty close. Since you say you are all thrill seekers, you should realize that UO is a thrillseekers paradise. We have been taking my thrill seeking DS 13 to Universal since he was 7 and I can't even get him interested in going to Disney! I think between the two parks you will have a nice time of it without venturing over to see the mouse. If it is within your budget, I would stay onsite so you can take advantage of the Front of the Line privileges (FOTL). The Hard Rock Hotel is usually pretty popular with teens, but you can't go wrong with any of the on-sites. I read on these boards that they are as good or even better than the Deluxes over at Disney.
I am not sure what the ticket deals will be next December. or how long you will be staying, but you can usually get a five day ticket for a pretty reasonable price. With the flexibility of unlimited access to the parks over a multi day period and FOTL, you and your daughters will have plenty of time to enjoy the parks and relax at the resort as well.
Unlike Disney, everything is within walking distance. The Royal Pacific Resort and Islands of Adventure are at one end of the complex, City Walk--restaurants, shops, nightclubs--is in the center with Universal Studios, the Hard Rock Hotel and the Portofino Bay Hotel at the other end. There is a water taxi that will take you from place to place, but for the most part you can get from place to place with an easy 10-15 minute walk. If you want to get from the parks to a restaurant at City Walk you are looking at a 5 minute walk. A walk from PBH to Islands of Adventure might take 20 minutes.
In the event you start yearning for the mouse, you can always take a day trip over to one of the WDW parks.
As far as where to start...stay tuned to these boards. Most here would agree that you will do better price wise to piece your vacation together yourself rather than buy a package. Kelly Monaghan has a great book on Universal that I first checked out of my local library, but have since purchased. You may also want to look at UniversalOrlando.com if you haven't already done so.
If you have specific questions, post away!
