Reddit mentions of Better Than Peanut Butter & Jelly: Quick Vegetarian Meals Your Kids Will Love!

Falafel pitas. In fact, anything pita is a sure-fire hit. Hummus is a classic, but nearly as certain a thing.
My kids are incredibly of veggie platters with fresh vegetables and fruit, but YMMV greatly.

Scandinavian-style open sandwiches with ultra-wholegrain rye is what kids eat more or less every day here in Denmark, and there are many many options for meals tucked away in there - tomato/cucumber sandwiches, cream cheese, the list goes on. Hell, my son eats salad sandwiches - as in, leaves of salad as the main ingredient.
SOUP! A great winter favourite here is potato and Jerusalem artechoke, sprinkled with a bit of thyme and roasted sunflower seeds. Drool.
Samosas and other filo-pastry constructions are awesome. Tempura'd veggies can also have that junk-appeal while being really quite healthy.
Different kinds of veggie patés can be made in bulk and used as a spread with tons of umami.

For further inspiration:
http://www.amazon.com/Vegan-Lunch-Box-Animal-Free-Grown-Ups/dp/1600940722/ref=sr_1_1?ie=UTF8&qid=1322338465&sr=8-1

http://www.amazon.com/Vegan-Lunch-Around-World-International/dp/0738213578/ref=pd_bxgy_b_img_b

http://www.amazon.com/Better-Than-Peanut-Butter-Jelly/dp/1590131223/ref=pd_bxgy_b_img_c

- all worthy investments - hell, they show up as "frequently bought together" as a big lovely set.

BUT I will say that the best best best way to approach this, and the one that will really make things cool is to engage the parents of these children in a dialogue about their children's diet.

I understand what your son probably means by too much flavor: Indian and Thai dishes have pretty complex flavor profiles and a lot going on in one dish. For a person who is still learning what tastes they like and don't like, complicated flavors make it hard to understand what you're tasting.

I raised my kid vegetarian until he took the opposite path: around age 6, he decided he wanted to be an omnivore. He still prefers vegetarian food, and it's what I cook at home.

I bought the original edition of Better Than Peanut Butter and Jelly when he was a toddler. It has a lot of recipes with simpler flavors that appeal to kids and adults alike, and most of them are pretty quick to prepare, too. What I frequently did was make the recipes with less seasoning, set aside a portion for my child, then spice up the rest of the dish to my taste.

My kid is 14 now, and is a much more adventurous eater – he enjoys eating dishes so spicy that they make adults cry.

I'd like to recommend a couple useful books:

http://www.amazon.com/Raising-Vegetarian-Children-Health-Harmony/dp/0658021559/ - my favorite

http://www.amazon.com/Better-Than-Peanut-Butter-Jelly/dp/1590131223/ - kid-friendly recipes

http://www.amazon.com/Vegan-Lunch-Box-Animal-Free-Grown-Ups/dp/1600940722/ - great lunch ideas

http://www.amazon.com/Vegan-Lunch-Around-World-International/dp/0738213578/ - ditto

http://www.amazon.com/Raising-Vegan-Children-Non-Vegan-World/dp/0972510206/ - may also be helpful, but personally I found it quite preachy and medically inaccurate at times