Castaway Joe's.....is that the Grouper Pavilion where they have basketball, ping pong, etc. (I was not familiar with it being named Castaway Joe's...I have always heard it as Grouper Pavilion) but anyway...yes, there are chairs and umbrellas though not directly adjacent to the pavilion...you would need to drag a chair to the pavilion area. You could just set up camp by the water and keep an eye on the pavilion.
It is a hike from the ship but a nice area.
MJ