ALways done waterparks, no issue. I think a properly taken care of water park is a very low risk. Heh I would avoid the kiddie area.
Really though it breaks my heart to see so many people not letting their kids do things because it might be a risk. Water parks, horse back riding etc. Kids have to have fun. Sure you can keep them locked in the house but quality of life matters for something, not just quantity. To a point you have to let go and let them do things even if there a slight risk to it.
I rode horses, went to water parks, we had a swimming pool, swim in lakes and oceans and rivers, did gymnastics, went to amuesmant parks, camp(not CF camp), played in the dirt etc. I wouldn't trade any of that. Would I be healther or had less infections if I wouldn't have done some of that? I don't know and I don't care, I know I had fun and that I have fond memories of it all. I still routinely swim in the river, ocean and lakes and go to a waterpark atleast once a summer.