First ... almond butter works great if your child is allergic to peanuts. You can purchase almond butter in most grocery stores and, in some stores, you can grind your own almond butter, as well as your own peanut butter.
With health in mind, go with low-calorie whole grain bread, if possible.
Spread on peanut (or almond) butter and add banana slices, dried fruit like cranberries or raises, crushed pecans or sliced almonds, and a teaspoon of honey.
Slip some baby carrots or celery sticks in a sandwich bag, as well as a few grapes. Include a thermos of skim milk.