OP Please excuse me if this has been said before, but there are many vegetarian dishes that can be cooked in about 10 mins by most teenagers (or perhaps by you while waiting for your meat to be ready), and eaten with whatever green veg/other veg the rest of you are eating. Plus carbs of choice.
-Piperade
-Egg pasta with peas and/or leeks and/or mushrooms plus soft cheese stirred in (there are many more possibilities)
- Stir fries - eg greens, red pepper plus cashews, flaked almonds or tofu (but again many, many possibilities)
- Welsh rarebit
- Pitta bread filled with felafel (bought), hummus or tahini, salad...
- Bruschetta with mediterranean veg (peppers in jars and similar tinned/bottled veg are excellent for this)
- Grilled or fried halloumi served with french beans and salad
- Griddled/sauted (can't do accents) veg (eg courgettes, broccoli, sliced tomatoes etc) with feta
- Baking potatoes microwaved until just cooked, halved, brushed with olive oil and grilled until golden. Serve with coleslaw, salad, grated cheese or even, from time to time, baked beans
- Savoury pancakes - Korean recipes are good for this; some use chick-pea flour which is very nutritious. Potato pancakes also good.
- Sweetcorn or courgette fritters
- Those 'ready to steam' packs of veg served with tahini/sesame/garlic dressing and tofu or a soft-boiled egg if liked
- Endame beans or broad beans (cooked from frozen) with soy sauce and ginger dressing and sunflower seeds and cooked greens
- Cauliflower or broccoli or similar stir fried with garlic and chilli. When almost cooked, stir in some peanut butter and enough water to make a thick sauce, plus soy sauce to taste.
And a whole world of other possibilities if you are prepared to use those pre-cooked packs of rice, lentils, fancy grains, etc etc. Serve with a variety of different dressings (based on olive oil, sour cream, yoghurt, tahini etc) with lots of steamed or stir-fried veg. Nuts and seeds sprinked on top add extra nutrients
- In the summer, dips made with (tinned) butter beans, chickpeas, canelloni beans etc etc, or three bean salad, served with crudites and green salad.
If 20 -30 mins are allowed then even more possibilities - roast veg of all kinds and combinations served with plain yoghurt or grated cheese, frittata, and, if teens can learn how to make simple pastry or scone dough - or use ready rolled pastry - quiche, veg tarts, pizza sorts of things
And soups in 20 mins if you have a simple stick blender - pea, carrot, leek and potato, mushroom, tinned lentil/bean/chickpea/tomato etc etc served with seedy bread and a piece of nice cheese.
Personally, I really dislike Quorn and all the other meat substitutes; to me they taste like cheap processed meals. IMHO, fresh food is nicer if possible. But some people must like them, because they seem to be everywhere.