Ever since I've had kids, since kid #1 has always been particularly picky regarding the entrees we serve, I've been perfecting the skill of hiding veggies in food.
For the most part, zucchini has always been my favorite. Shredded, the stuff can be put in most anything and not be detected. If the green bits from the peel give it away, then peel the zucchini before grating it up. Zucchini bread, brownies, pancakes, oatmeal, cookies, muffins, meatloaf and pasta sauce all hide zucchini well. No taste difference at all.
Grated carrots and fresh spinach leaves that have been frozen and crumbled (grab a handful of frozen spinach leaves and crumble into anything you are making) are other favorites. Cauliflower that has been pureed or chopped finely works good since it's white.
BUT. I can't believe I've overlooked one of the most versatile veggies all these years. My oldest child is 11 and 1/2, so that's a lot of years. CABBAGE. Yes, cabbage, folks. Cabbage is inexpensive as well. Use some of the head to make cole slaw if your family likes that. The rest can be shredded or chopped and added to recipes. I added some to Rice-a-Roni fried rice flavor and my kids didn't even notice it was there. Dh liked it better with the cabbage than without. Add it to soups, casseroles, and stir-frys. You can buy the already shredded coleslaw mix if you wish, but I just buy a whole head. It will last for a while. Cabbage is fairly easy to chop, or it can be grated in the food processor and stored in a Ziploc bag.
Yes, Cabbage Works For Me.