We don't let the kids go anywhere near the water on Castaway, especially since we don't connect to it! So don't worry- the kids don't get to swim with us (but they do get wet in our fountain splashpad! )
Security is taken SO seriously on Castaway, to the point where you can see many of us physically standing by all gates and borders all day. We call this 'glorified security guard duty' and don't really get to interact with the kids - but! Don't think we're just standing around alone! We're an added line of security defense for the kids!
What you should be concerned about is sunscreen. Put loads on. Maybe give a little bag with a travel sized one and teach your children how to apply it. For maaany reasons, we aren't allowed to ever be seen applying sunscreen to a child!