I've also rented one before, only had 3 people though so it was very comfortable. Be "careful" with the drinks because technically no outside alc. drinks are allowed, however we did bring our own bottle of prosecco. Our strategy was to buy one of the drinks (per person) that you're brining to the pool so you can get the respective cup it comes in, then just be careful not to be seen pouring refills from the bottle (or can of beer); this way you're also at least buying one drink from the bar.
I can't remember exactly what happened, but I feel like you can reserve exact cabanas because by the time we checked in (10:30/11am), the attendant said all the good ones were already reserved. I would just call and ask.