Ok. Thought of a few more japanese-y veggie dishes. My children love japanese-y food.
You could do tofu in teryaki sauce (not traditional but my children love teryaki sauce, although we often have teryaki chicken or beef). You can buy the sauce in a jar but it is very easy to make. Mix up 125ml soy sauce, 125ml mirin (you can buy this in sainsbury's, but it's much cheaper in oriental supermarkets or online) and 2 tablespoons of sugar. Bring to the boil and then let it simmer for a couple of minutes (you can actually achieve this in the microwave if you don't want to wash up a pot).
Tofu with sweet miso sauce: Mix up the sauce from 3 tablespoons red miso, 1.5 tablespoons sugar, 1 tablespoon mirin, 2 tablespoons stock (the Japanese use dashi, but you can substitute veg stock) and 1 tablespoon of sake (I never have sake in the house, so you can substitute sherry or Chinese rice wine or just more stock; it's fine). Grill thick slices of firm tofu for about 8 minutes, then smother in a sauce made from 3 tablespoons and cook until the sauce is warm.
You could also make a version of chicken and egg donburi (which my children love, love, love) using tofu cubes instead of chicken. Cook some Japanese rice (which my children like better than long grain rice because it sticks together). Make up the sauce in a pot. You need about 250ml of stock (you can use a half and half mix or sake and stock if you like, but I don't), 50ml of soy sauce, 3 tablespoons of mirin (substitute for sugar if you don't have any).
You poach the tofu (or chicken if you're using it) in this sauce. When it's pretty much done you pour in 4 beaten eggs stick a lid on it, turn the heat off and leave it to stand for 2 or 3 minutes. This will cook the eggs. You can throw in some spring onions before this, or after it too. To serve, put mounds of rice in deep sided bowls and ladel the sauce over this. It looks a bit odd but tastes fantastic.
Takikomi rice is also nice: wash 2 cups of Japanese rice (always wash Japanese rice before cooking, as it's very starchy) and put it in a heavy bottomed pot with some diced carrot and sliced mushrooms (or whatever veg you like really). Make up the cooking liquid from 3 tablespoons soy sauce, 1 tablespoon mirin and (optional) 1 tablespoon sake, with enough water or stock to make up to two cups of liquid. Add the liquid to the pot and bring to the boil with the lid on. Once it's boiling turn the pot right down as low as you can for 15 mins. Then turn the heat right up for about 30 seconds before turning off and leaving for 10 minutes. Don't take the lid off at any point during the cooking process. Once it's done, mix everything and serve.
You can do a kind of vegetarian barbecue thingy too. The sauce is easy: 2 tablespoons soy sauce, 1 teaspoon mirin, 1 tablespoons sesame oil, I tablespoon chopped garlic. Pan fry or grill something with a meaty texture, like slices of aubergine or you could grill slices of tofu. Add the sauce when it's done and let it heat through.