The Ama Ama Upper/Lower Decks are located to the far left of the Ama Ama deck (if you are looking out to the lagoon). It is a little secluded...which was nice for us. We spent most our day in the hustle and bustle around the pools/slides. We enjoyed having a quieter place to retreat to. Everything is really close...you do not have to walk far to go between the pools, slides and lagoon.
When we had our larger group, we did 2 cabana days (by the Menehune Bridge) and one day with the EL. When DH, DD and I went back March 2015, we did the Ama Ama deck 2 days, since it was HI spring break. I enjoyed spending the day in all 3. I know people that gave booked all of the above at the 10 month mark. If you are interested, I would do it asap. They do not require a deposit.