You’re doing a great job OP. I hope some of my ideas are useful:
Tortelloni with tomato sauce just to vary it a bit!
Make your own pizzas. Buy wraps or pizza based and passata. Top with pre cooked things eg ham, ready cooked chicken, olives, sweet corn, cheese. In oven roughly 10 mins or until cheese is bubbly.
avocado / cheese / eggs / baked beans on toast. Serve with any veg
pesto pasta for sauce variation! Less healthy though so add more veg to side
Do they eat fish fingers? Can be pretty healthy with any potatoes + veg they like
Falafel, humous, pitta
Halloumi burgers. Just fry slices of halloumi and add to buns with lettuce and tomato.
Omlettes
Jacket potatoes (long time in oven but then easy prep) with easy toppings that they pick themselves - tuna / cheese / salad / ham / beans etc
Veggie sausages and mash / chips (make yourself in oven)
my overall rule for dinners is a protein a carb and 2 veg. I find it easy to figure out meals from random things this way! Fruit is snacks and breakfast for us usually.
eg I’ll serve maybe some pre cooked chicken, pitta breads, cucumber and carrot sticks one day then sausages, chips, peas and broccoli the next.