There are grills and tables, not sure about bringing your own grill. we saw several kids in the creak.
Picnic areas have tables and the usual big square grills. Camp sites have fire pits with grills attached. You can bring your own grill.
The Rangers told me that swimming and boating aren't allowed, but they didn't say anything about wading. They have firepits with grills at the campgrounds and I think there are elevated grills at the shelter near the Visitor's Center.
Not sure about the grilling situation, but yes there are some places where kids can play in the water.
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