You are too good! That is much easier than the method I used.
Just don't forget to add the tax. Not a high percentage, but still.
Experiences seem to vary. Some get quoted the difference between what they paid and the price for the upgraded rooms. More seem to report having to pay the difference between rack rate (normal rate before discount of any kind) for the booked room and rack rate for the upgraded room.
DO NOT!!!! I repeat DO NOT!!!!!!! take this as a fact or given of a free upgrade. IT IS NOT! OK, we're clear on that one?

The AKL apparently doesn't have many standard view rooms. At certain times they'll oversell those, and upgrade some guests into savannah view rooms. Seems to happen more frequently than roomtype upgrades at some other resorts, but still very much luck of the draw.
At AKL I'ld book what I'ld want. For those that see AKL as a 'need savannah view'-resort to really enjoy the theming it is very not smart to play the upgrade-game. Even if you want to pay full price, availability might be zero. The longer the stay, the more difficult it'll get anyway.
I've done AKL with savannah view, well actually did AKL CL which comes with savannah view. Had my location request filled, overlooking the main savannah from a great spot. Loved the view from my bed (sitting up) and balcony. Having a munch out there and enjoying the animals. Having said that; the resort offers many places to enjoy the animals if you haven't got a savannah view room. The savannah view was a nice perk, absolutely. But if having to pick? I'ld do CL without savannah view before I'ld do savannah view without the CL.