You need to cut back on meat and only have it about once or twice a week really. This is where most of your spending is.
If you buy a large chicken and roast it, plate it up so that people cant start picking at it and then you will have enough for a pie the next day. Bulk the roast up with lots and lots of vegetables and then everyone will have enough to eat.
This could be your week of food
Mon - Roast chicken and vegetables
Tues - Cauliflower Cheese and vegetables
(Cauliflower Cheese is the main part of this meal as there it is quite filling and you dont need all the other stuff you usually serve with it)
Wed - Chicken Pie and Gravy with vegetables
(made from the chicken from the roast)
Thur - Sausage and Mash and vegetables
Fri - HM vegetable soup - made with any leftover veg from the week
Sat - Spaghetti Bologanaise
Sun - Leftovers or a curry or something with lentils
You also need to train the family that you are on a budget and they are going to have to eat what is provided or do without as you are not a restaurant serving different meals for everyone!!