Invitations

Cut out wavy ovals out of blue posterboard.  Then write in your party info, including "don't forget your swimsuit!".

or-- Inflate a beach ball and write in permanent marker, "Join us for a pool party!" - and the rest of the party info.  Deflate and mail or hand deliver to guests.

tip:  you can also remind them to bring their favorite water guns, and balloons for water balloons...

Menu

Serve hot dogs, hamburgers, watermelon, etc. (easy stuff that you can prepare outdoors -so you don't miss any of the fun!). You can also serve potato or macaroni salads in kid's sand pails. ~of course use only new pails, and sterilize completely.~

Fill big galvanized steel tubs full of ice and hide frozen 'Pop Ice' in the bottom to keep frozen for cooling off later, and put cans of tea, lemonade, and soda sticking in the ice on the top.

You can also make your own sno cones. 

For the cake ~just make a sheet cake, and frost all with blue-green frosting.  On one side, make 'waves' with your knife or spatula.  On the other side, break up graham crackers into 'sand' and sprinkle on for the 'beach'.  Next, add palm trees, beach balls, etc.. You can also add Teddy Graham cookies and dress them in bathing suits using small gel frosting. Lay them on the sand - to 'sunbathe'.  Palm trees, beach balls, etc. can be found at your local cake decorating shop.

Decorate the yard with tiki torches, big pots of flowers, and lots of big beach balls in the pool...

Activities

Set up pool volleyball, or other pool game for a group.

-----and don't forget:

Practice safe pool fun-- make sure an adult is on 'lifeguard duty' at all times.