Hi R.----I think that most of these suggestions are valid and you will just have to find which method works best with which foods. But kids a quick to learn and you will have to adapt quickly to stay ahead of them.
Hiding veggies in different foods, I really like to put lots of different things in smoothies, I think is a good strategy for the short term. There is a will known process called metabolic programming. By that, every cell in the body recongnizes when it gets good nutrition, and, after time, starts to crave those veggies. So, after sneaking the veggies in other foods, while at the same time offering them to your kids on their plates, your kids will start to eat some veggies.
I too, believe that you should require at least a bite or two of each new food. I tell my kids that cannot tell me they don't like something if they've never tried it. Then, I let it be...for that meal. I recommend spending a little time a www.askDrSears.com. Dr. Bill and his son Dr. Jim (the ABC show The Doctors) have a great section on picky eaters. With loving PERSISTENCE, your babies will soon be great eaters.
Lastly, if you are concerned with their nutrition, I would like to share with you what my family does for fruit and veggie insurance. If you are interested, I highly recommend, as does Dr. Bill, a whole food supplement made of 17 different dehydrated juice powders put into capsules and gummies. Can you imagine how healthy you and your family would be 'eating' parsley, kale, cabbage, broccoli, carrots, tomatoes, beets and spinach each and every day? You'll have the 'Healthiest Kids in the Neighborhood'. (a Dr. Sears book) Speaking of his books, you should go get Eat Healthy, Feel Great. A cute kids book based on 'traffic light eating'. Also has a great chart showing red/yellow/green light foods. There are actually a whole bunch of kids books about healthy eating. Contact me and I can share some additional titles.
Good luck and keep trying. I look forward to hearing from you. Keep cool. D.