OK, so there’s a few ideas in this linked article, but take it from a dad of 4 very independent and iron willed veggie haters–none of this friggin’ works!
Except…one method that I used back in the day (not listed in this article). I would puree different greens, garlic, onion, carrots, zucchini, eggplant and other veggies and then lightly saute in olive oil. From there, I’d blend the mix in to their fave bottled pasta sauce and then proceed with spaghetti and meatballs (turkey meatballs – that was trick # 2) as normal. They loved my “secret recipes! And I don’t think they knew my tricks–until now, haha.