fresh fruits and veggies are perfect. sliced apples or pears or peaches, a banana, grapes, an orange
or dried fruit: apricots, rasins, prunes (anything without added sugar.
veggies with ranch dip: baby carrots, cucumber sticks, cherry tomatos, cerery
celery with peanut butter or cream cheese
personally me and my son LOVE plain yogurt (not vanilla because it has added sugar) with rasins (they add natural sweetness and fiber) and chopped nuts mixed in. (walnuts or pecans are the best)
all of these are easy, nutritious, and delicious. keep the the kinds your kids like on hand all the time.