The one thing I find interesting about that statement is that by virtue of the fact that waterslide height requirements aren't very high, I'd argue that waterparks are quite family friendly by default. Certainly more so than theme parks, anyway; even most big waterslides have quite wide family appeal.
With that being said, Chessington are a young families' resort, so I can see their rationale behind not whacking up huge drop capsule slides and funnel slides and such.
Perhaps this will be something like the Center Parcs Subtropical Swimming Paradise format prior to the recent installation of the massive water slides across the board? If it were something along those lines, it wouldn't be a huge water park, but it would certainly be a fun supplement to a Chessington hotel stay!