Seems like you're asking an open ended question.
It the destination is an indoor water park such as Great Wolf Lodge, leave your pistol gun in your luggage or room. Car is a no-no.
If you're thinking a roadside economy, no-tell, mo-tail, you and yours are more vulnerable when you are wrangling kiddos and gear from the car to behind the door of your assigned room. Again, car storage isn't a great idea.
As to the water attractions, we have a full plate keeping up with key cards, credit cards, ID, and kiddos w/o considering side arms.
The safest place for side arms is on your side. Just maybe not in a water park.
Bread and Circuses don't pay the Bills.