Here's how Stephanie sneaks in greens:
My 21 month-old son refuses to eat leafy greens but has no problem gobbling up cheese and carbs. No surprise there right? I have figured out a way around this. Before preparing his mac and cheese, I take the amount of water that the box calls for, heat it and put it in the blender. I then throw in some frozen or fresh spinach and puree the heck out of it. Then I put the spinach water puree in a bowl, add the mac and cooking it as per the microwave instructions then adding the cheese. Other then it being green, he has no clue there is spinach in it, which he would normally never touch. The green mac and cheese tastes pretty much just like without. For older kids, you could maybe say it's Oscar the Grouch mac and cheese or Martian mac and cheese.
I also add spinach to smoothies, and no one's the wiser. Hope this helps!