Frozen strawberry yogurt snacks - You can make them by dipping strawberries (halved or whole) in vanilla yogurt (Greek might be best, because it's thicker), then putting on a sheet pan lined with parchment or wax paper and freezing.
Make colored sand art by stirring a chalk stick in a bowl of salt. it changes the color. Stir less for light color and more for dark richer color. (I used to do this with salt and food coloring. but the chalk stick idea is brilliant!
Leuk voor op de camping 's avonds. Just fill up a plastic water battle with water and put a glow stick inside and put the lid on. do this with a couple bottles then have a competition. Would be such a fun camping or backyard activity.