When did everyone become afraid to ask a parent, to abide by a rule? If you are right, than what can they possibly say? Just ask them nicely that you would like to enjoy the adults only pool, and if by chance they to not oblige, get an appropriate person to handle it.
On the other hand, those kids are paying passengers also, and some of those kids have paid the 1st and 2nd person rate, so they have paid the same amount as you. They are not afraid to take over the whirlpool, so why are all the adults afraid?