There are so many different grains and beans, and it is fun being vegetarian if you experiment with cooking different ones. Some of our favourites are: black turtle beans, pinto beans, puy lentils, red lentils, red kidney beans, navy beans, then there are aduki beans, black eyed peas, yellow split peas, giant Greek beans, etc, which I cook less often.
We have about 4 or 5 different kinds of rice (my favourite is short grain brown rice), amaranth, whole oats, millet, barley, polenta, quinoa, bulgar wheat etc.
I make different soups, stews, pies, wraps, and so on.
I also use nuts, seeds, lots of herbs and spices, and many different vegetables, as well as tofu, seitan and tempeh.
We eat some cheese and eggs, but not an enormous amount.
Our diet is fun and varied, I think, mainly because I enjoy fooling around with different ingredients. At the same time I am very lazy and never take a really long time to cook anything, and never can be bothered to follow a recipe accurately.
(Thanks for not minding me saying how great my kids are. I hate to come off as smug, but there are always lots of people who thing vegetarians are self-righteous, sickly, flabby, joyless prigs. I guess I want to defend vegetarians from all those accusations. Vegetarians are just like everyone else: some of us are annoying all of the time, some are annoying some of the time, and some are hardly ever annoying.)