I use my coffee grinder a lot...and not for coffee :)
When I see the most common "deceptively delicious" type recipes, they generally involve sneaking in pureed fruits and vegetables. What I also work on sneaking in at my house is more beans, brown rice, oats, flax, and other grains. I find it very easy to do with my coffee grinder. A half cup of steel cut oats that has been grinded to a fine flour takes seconds, and is a lovely addition to pancakes, breads, etc., without the typical oat texture.
Beans and grains together are a whole protein. A quarter cup of dried black beans and a quarter cup of brown rice grinded and added to supplement the flour in brownies adds nutritional value.
Grind up your flax and sprinkle it into oatmeal, stir into yogurt or smoothies.
My kids never notice a thing.