(Image credit: Apartment Therapy )
Take home a little bag of sand from your vacation and let the kids add it to any small box with a few rocks and a fork and you'll have an instant Zen Garden.

Depending on your box, you could also make a really large one of these and keep it outside on a picnic table for the kids to redesign from time to time. Also makes a cute, homemade teacher gift if you happen to be looking for one of those. We found the activity here.