Stir fry with tofu and/or cashews and rice or noodles. You could do prawns separately for the pescatarians, and use Chinese, Japanese, or Thai flavours and make it as spicy (or not) as you like.
Tomato, minestrone or vegetable soup with cheese toasties.
Taco soup - basically a runny bean chili base loaded with nacho chips, avo, salsa, sour cream, cheese, and whatever other toppings you like.
Mac 'n' cheese with pureed butternut squash mixed into the cheese sauce and extra broccoli, baby tomatoes, spinach, or whatever veg your DCs will eat. You can also stir through tuna for the fish eaters.
Roast dinner with cheese souffle or cauliflower cheese instead of meat for the veggies.
Sauteed gnocchi with pesto, mushrooms, baby tomatoes and spinach - if you buy ready made gnocchi and pesto this can be on the table in 10 minutes.
Lentil shepherd's pie with either mixed root vegetable or regular potato mash.
Linguine arrabiata with baked or fried breaded aubergine slices. You can also add quorn meatballs.
If they like aubergine you could also do Imam bayaldi, lentil moussaka, or aubergine parmigiana.