M.D.
Don't forget the sunglasses----there is a lot of glare off of the sand and the water. We used a little sunshade tent--that worked great...it is just a little semi-circle "backwall/roof" attached to a circular bottom. It provides shade and keeps the sand out if it is really windy...plus the little ones like that they have their own little "place" to hang out. And unlike an umbrella, you can position the tent to face any direction so that it has shade.
I would also suggest a mesh laundry bag. You can dip everything into the water to get rid of the sand, and then it can all air dry in the bag. Also great for collecting shells (if you are at the ocean),