There are so many different places to sit. For us, personally, we enjoy getting several lounge chairs together behind the beach area, where there is both sun and shade and picnic tables.
If you have young children, you might want to sit at the kids area or grab some seats right along the beach area.
Have fun! The most important thing about finding chairs is to get there early. During the busy season, this means right when it opens or wait until about 3ish, when people start leaving.