Here are some ideas for a simple party, perhaps for a summer birthday.
Make A Watermelon Cake
Bake one rectangle and one circle. Cut the circle in half.
Put one half circle on each end of the rectangle.
Frost with green icing. Enjoy!
Make Watermelon Balloons
Use a permanent black magic marker to draw some seeds on dark pink balloons.
Decorate with the pink balloons and with green balloons.
Make A Watermelon Fruit Basket
Hollow out a watermelon and fill it with summer fruits for a refreshing treat.
Play Watermelon Games
What is more natural than a seed spitting contest?
Or dry some watermelon seeds in advance and make collages.
Or play a Pin the Seed on the Watermelon game.