17th Birthday Party

In august is my seventeenth birthday. I always plan my own or it will never get done. I am having guys and girls at my party possibly around 20. Several of them will be staying the night. I need to figure out what to do for the day with my guests so it isnt JUST a sleepover. I want everyone to have fun and i want to keep the cost down. Also a few of the ladies are pregnant so i need to keep them in consideration. I really have no clue what to do can someone please suggest something. Thanks