I've got similar aged boys (2) but we are pescatarian and I use quorn quite a bit in cooking- the mince, sausages etc, along with fish.
I tend to be a bit boring with weekday meals, pasta bake with tuna and mascarpone sauce (£1 sauce from Waitrose, tin of tuna, some pasta) with some tinned sweetcorn in its and veggies (usually carrots and broccoli)
Then another day spaghetti bolognese with quorn mince (about £2.50 a pack or less) with bolognese sauce (again £1 Waitrose essential) and veggies
Another day might be baked potatoes and beans. Sometimes Friday / Sat nights might be shop bought pizza.
Dh tends to cook at weekends, he will make home made fish fingers for which I tend to buy hake fillets as a bit cheaper (about £4.50 for two) or home made fishcakes with tuna - again not expensive and uses up tins of tuna in the cupboard.
Not sure if we are quite as healthy as you- maybe a bit more reliant on carbs and I know some people criticise veggie (quorn) stuff as processed, but for us it is a source of protein.
Another quick meal they like is the filled pasta (fresh) again Waitrose essentials.
I do have some health problems and struggle with cooking much so things tend to be quite simple. I have my own fresh ready meals from Frive as I am on a diet right now, they are about £40 a week, Dh tends to cook his own dinner (eggs and salmon mainly with some tomatoes / veggies most nights)
I get a weekly delivery form Waitrose on Friday and the is £2 for the delivery which I think is really good.
Some treats we have is Dh really likes camembert cheese so we get one of those (about £3) and the Charlie Bigham's fish pie. often when it is on offer as £10 otherwise. Boys usually have that and DH a bit (not a big eater)
We spend around £100 - £150 a week, (for the weekly delivery) which includes e.g. washing powder and shampoo etc with top ups on top.