Get a Field guide and try to name every plant and tree in the area.
Keep track of how many you find.
Learn how to make a fire with out matches or a lighter, its easier than you may think.
Again a Field guide for birds. bring a pair of binoculars and see how many you can name.
Mark the shadow of a stick at hourly intervals from morning to dusk, you will see the arch the sun takes through the sky. You will also discover how to tell the four directions north south east and west by just looking at the sun and noting the time of day.
If you do just the things I mentioned you will fill your time.
bonfire
s'mores
scary stories
hide and seek
hike
check out wildlife
stargazing
play frisbee
card games
board games
football
sand castles
Just some ideas, im an avid camper and this is the kind of stuff my family does other than swim and fish because that is a little obvious, right?
me and my family used to go camping a lot,
so to keep entertained,
my parents always brought:
-games
-soccer balls/ football
-IPOD! ( cant forget)!
and tanning chairs.
While your camping you can make smores, sit around the campfire, tell scary/funny stories, hike, and a lot of other things to. Theres always something to do when your camping.