C.,
Smoothies are the way to go. Quick. Easy; as healthy as you want them to be. The fruits overpower the greens and other things you can throw in, making them tasty enough for a child to like.
First, go to Walmart, kitchen appliances section, and get a Hamilton Beach immersion blender, cost about $20.00. It is very sturdy, well-designed, easy to rinse to clean, was fabulously rated a year ago by the Star Telegram in a Consumer Reports-type test as to the best blender for the smallest amount of money. Then get a tall-ish narrow container to use it with, something about the size of those things you see when they put a container into the blender malt-shake machines at Braum's, etc. Holding about 3 cups to a quart.
Then, don't think of smoothies as needing specific recipes, but more as a type of food: use whatever you have on hand. I buy the Knudsen bottles of juices to keep in the fridge and add a splash (about 1/4 cup) of whatever I'm wanting. I add a milk-based thing if I want that, for probiotics, such as plain kefir, yogurt, or even milk; another 1/4 to 1/2 cup. Then I add various fruits, fresh or frozen. Keep bananas in a zip-type bag, peeled, halfed, frozen, using up the ones that are getting toward the edge by peeling and throwing them into the freezer, then grab a half to throw into your smoothie. It's the texture and taste of ice cream and gives smoothie a creamy texture. I keep a huge bag of frozen blueberries in the freezer, and thrown in a 1/4 to 1/2 cup each day...all those phytonutrients and antioxidants! Strawberries, raspberries, mangos, peaches, etc. I will also use fresh fruits, grapes (with skins), berries of any kind. Apples, even citrus. Whatever fruits you like or have, or need to get rid of. Everything goes into the container and gets blended.
You can buy a whey-type protein powder. Sam's has a 5 lb bag of EAS vanilla or neutral that will last forever, adding one scoop per smoothie, IF you want protein, and I'd recommend it...as it makes it more filling. Or you could add in a raw egg. I buy organic eggs, cage-free/free-range, and have NO fear of consuming a raw egg from chickens treated well.
Finally, a big surprise...you can also throw in fresh greens of all kinds, sprouts, spinach, lettuce, the salad combos that come in bags...the blender renders them all invisible, tasteless (masked by the fruit flavors). You can add a 1/4th of a ripened avocado, also for smooth creamy texture, taste disappears, but you are getting the raw nutrients and phytomolecules of all those vegetables right along with the fruits. Almost any combination works. I buy Oodwalla Superfood, the big bottle, and it lasts for weeks in the fridge (this is a delicious fruit-based greens drink that's wonderful by itself), and throw in a half-cup of that when I don't have greens on hand.) This combination will make from 2 cups to a quart, depending on how much you pour in of each thing.
Next, another neat surprise, if this is more than you want in a single breakfast, you can pour the extra into a popsicle maker and have them as pops for your boy, or yourself, as a healthy, refreshing snack later.
There's no magic, and no specific recipe, just a way to consume a lot of fresh/frozen fruits/vegetables and protein in one setting. Awesome tastes. You can begin to make specially-oriented ones, like pineapple, coconut, banana...to get a pina colada-tasting one. A citrus-based one using oranges, grapefruit, etc. A melon-based one, using cantaloup, mango, papaya, watermelon, honey-dew for that taste range. A banana-strawberry-blueberry one. The range of options makes it easy to vary and not get tired of any of them.
You get rather good at trying new combinations, gradually learning the combinations you like the best and want to remember.
It's a meal that is mainly raw, fresh, can be organic, VERY healthy, easily assimilated, and completely satisfying, especially with the protein powder for substance.
Once you get practiced at it, you can throw a great smoothie together in about 5 minutes, pour the leftovers into the popsicle-form, rinse off the blender blade thing, and you're done.
Enjoy!