Hi J.,
I've been vegetarian for a few years, but I only have one child. He's 15 months old, so he pretty much eats whatever my husband and I eat. I don't know how kid friendly my suggestions are, but I'll help as much as possible.
If you eat conventional produce instead of organic, look for a Joe Randazzo's market in your area. They have really inexpensive produce, but they don't usually sell organic (There's one in Macomb, Roseville, East side of Detroit, Westland, Redford).
In my house we eat lots of bean dishes. You can get a bag of dried beans for about a dollar, soak them overnight, rinse them in the morning, let them cook in a crock pot during the day, and use them for dinner. They also freeze well. They make great soups, put them over salads, cook them with vegetables, put them over rice. Beans offer lots of fiber and protein. When you combine beans and rice, they are a complete protein just like meat. I buy brown rice from Randazzos when I buy fruit and veggies. $3.69 for a 5 lb. bag. You can also use beans in burritos, taco salads and lately I've been making lots of wraps (using black or pinto beans, rice, sauteed veggies, and homemade guacomole).
We do stir frys. Sautee some fresh veggies (or frozen veggie blends) w/ onions and garlic, a little firm tofu cut into cubes (doesn't really taste like anything -- offers protein). We like bell peppers (colored ones are nice :), mushrooms, broccoli, green beans, peas. Whatever you have on hand. You can buy stir fry sauce, or I make a sweet & sour sauce w/ water, a little ketchup, white vinegar, soy sauce, lemon juice, and a little cornstarch to thicken.
Spaghetti w/ lots of veggies (peppers, mushrooms, olives...). Occasionally I use ground boca or morningstar crumbles as a meat substitute. Some say be careful giving too many soy products to children. I've heard conflicting advice about it, so I need to do some more research. You may want to as well.
Spinach or veggie lasagna. Sautee spinach or some other veggies and mix them in w/ your ricotta when you make lasagna. You may use veggie crumbles here as well. Stewed canned tomatoes are nice.
I don't use a lot of canned vegetables, but canned tomatoes are excellent. Some say they are better than fresh b/c they are actually vine-ripened instead of ripened in a box on the back of a truck somewhere.
If you do eggs and dairy, those are also great sources of protein. For some reason, we have this protein obsession that we don't need to have. Eat a variety of foods and don't worry too much about it. You'll get plenty. We can get protein from the same places the animals get it.
If I think of anything else I'll write more later. Feel free to contact me if you have any further questions. Good luck!
H.