Set up a "Beach" in your backyard. Have a pool, sand box, individual tubs for each child. Let them put water in the sand box (sand in the pool?).





Have props for dramatic play: Beach towels, empty sun screen bottles, sandals, pails and shovels, beach umbrella, beach balls, fish and fishing poles, etc.





Play "beachy" games:

Beach Ball-- Have them roll it to each other (or toss).
Play dodgeball with older kids.
Have them keep it in the air and not touch the ground.
Go Fish--If younger kids can't hold a hand of cards, play with a draw pond. Instead of asking each other for pairs they set their hand on the table in front of them and then draw a card and see if it makes a match.
Use the cards for concentration
Or play Ocean Animals Dominoes
I also have some luau stuff (leis, straw hats, grass skirts etc) if we decide to have a luau party.

If you can get a Fisher Price Pirate Ship that is fun to use too. I want to add a day on pirate fun!