Just to say I think it’s really sweet that your DD has asked you this and you sound likely a lovely mum!
Big pans of soup/stew - can add whatever to it. I like minestrone for lots of veg for and they can add GF pasta or make 2 separate pots. Can add beans for extra protein.
Thai green/red/yellow curry with tofu if all are OK with soy. Or Quorn pieces but check they are GF.
Paella/risotto/one pan rice things. Old El Paso do an amazing one pan rice kit for about £3 (but you could recreate if budget is needed.)
Curry with squash/pumpkin or sweet potato instead of lentils or meat, as PP mentioned meat could be added separately. Just double check any ready made curry sauces are cashew-free as they are in a lot of kormas etc.
Pad Thai! Rice noodles are GF as said above. Can get meal kits in Aldi as long as everyone is ok with fish sauce and peanuts (you could remove the fish sauce and replace with more soy if making from scratch).
Stuffed peppers with couscous! Family favourite here and so cheap.
Sounds counterintuitive sausages and mash, cottage pie, shepherds pie made with veggie meat alternatives like Quorn or soy protein or veggie sausages ofc. I’ve even had a veggie ‘Irish stew’ with sweet potato chunks and it was amazing! Add plenty of minced mushrooms, carrots, onions to bulk out.
Picky meals where they can all choose - kind of a mezze - stuffed vine leaves, olives, cheese, hummus and veg sticks, fruit etc. Meat for those that want it and bread in its many forms.
Spanish-style omelette/tortilla could work well to jazz up omelette nights a bit!
GF frozen pizzas are fairly easy to find now for an easy meal with salad.
Can housemate 2 eat beans that aren’t baked beans? That opens up a lot of doors.
As expensive as they are, M&S and Coop both have great Free From sections. Waitrose is OK, much better for vegan/veggie ready meals than GF stuff imo. Aldi’s frozen veggie stuff is amazing but a lot of wheat protein sadly!
Also recommend Bosh and the Mob Veggie cookbook - maybe an early Christmas present? 😉