Would the kids eat fish? It can also be a little expensive, but buying the 'family pack' is usually a lot cheaper per pound. Some other ideas:
-Veggie lasagna (same as usual, minus the meat, plus mix in whatever veggies you know the kids will eat)
-pita pizzas: I buy pita bread or you could probably use those sandwich thins that have become really popular. You can use a lot of the same ingredients from your pizza pasta, just put them on the bread and pop in the oven to melt the cheese and crisp the bread. The kids will have their own little pizzas and can mix and match toppings.
Can you work beans into dinner anywhere? You can buy those in bulk packages and cook them yourself for a lot less. Use what you need for dinner and throw the rest in the freezer to use later. They're packed full of protein and fiber.
You might have to think up some game to get them to try new veggies and maybe you'll find some new favorites. If you don't want to use meat, hopefully you could at least get a wide variety of veggies in them!