Our son is just like I was at his age: the only thing he will eat for lunch is a PB&J sandwich. We use natural crunchy peanut butter (Trader Joe's is the best), and good quality strawberry jam. But the bread is the most important part.
While the No-Kneed Bread makes delicious bread, it's not good sandwich bread. For that, I turned to the Bread Lover's Bread Machine Cookbook. Ages ago, my friend recommended this cookbook to me and it is awesome. Trying a few of the recipes, the "Light Whole-Wheat Bread" was almost there...but it was a bit too light, and I found the volume measurements to be a bit inconsistent. When baking, having a scale is essential. So I boosted the amount of whole-wheat flour, tweaked a few of the ingredients, and converted the volumes to weights, and voila!
The Best Whole-Wheat Bread-Machine Sandwich Bread
Makes 1 2-pound loaf (a week of PB&J sandwiches for a 4 year old)
2 1/4 cup (11 oz/310 g) bread flour
1 3/4 cup (8 oz/225 g) whole-wheat flour
1 1/3 cup (325 g) water
1 large egg
2.5 Tbs vegetable oil
2 tsp salt
2.5 Tbs dark brown sugar
4 Tbs buttermilk powder
1 Tbs wheat gluten*
1 Tbs bread-machine yeast
Warm water to luke-warm (I do 50 seconds in the microwave). Mix the dry ingredients (bread flour, whole-wheat flour, salt, brown sugar, buttermilk powder, and gluten) in a bowl. Add water, egg, and vegetable oil to the bread-machine pan. Carefully pour dry ingredients on top of water. Tap pan to counter 3 times to settle. Pour yeast on top.
Put pan in bread machine, and set to 2-pound loaf, regular/white bread, medium crust. (The "whole-wheat" setting will preheat the ingredients, but since this is less than 50% whole-wheat, this isn't necessary). Press start. Although bread machines are supposed to be "Set it and Forget it!" I find it's useful to help things along with a spatula in the early phases. Wait 3+ hours, and you'll have a delicious loaf of sandwich bread! (Sorry, you'll have to slice it yourself).
* if you don't add the gluten, apparently this doesn't make it gluten-free.