If you are into crafting you could pick up the $1.00 flip-flops at someplace like Hobby Lobby or Wal-mart and create embellishments with yarn, beads or paint.
You could make up slushie mix to have a colorful poolside treat. This is the basic recipe I use and I play with the Jelllo/ Juice flavors for fun I highly recommend a cherry-lime combo.
1 quart water
1 3oz. package lemon jello
2 c. orange juice
1 c. sugar
Mix water and sugar to boiling. Remove from heat and add jello. Cool. Add juice and freeze. Set out about 2 hours prior to serving so it will be easier to "slush". Use a knife or large fork to break it up into slushie consistency.
Also you could set up a foot scrub area to get your feet all summer ready using a kiddie pool full of fine play sand. Try this recipe http://www.bathandbodyrecipes.com/tip.php?tipid=780
Just some thoughts it sounds like you will be having a great time, good luck.