jeans or bermudas also can, polo shirt or shirt.
Can listen to songs (bring radio) etc, BBQ, can play card games,
also bring camera to take photos.
If at ECP or West coast, can rent bicycles, or blades. Can also
dump people into the sea. 
And also play water at the beach. Or even fishing.
Else, prepare some games to play, those community games, like
charades, guess the killer, etc where everyone seats in a circle.
